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The next season's new companion will be a returning character:
  • Shona from "Last Christmas", due to popular demand.
  • River Song.
    • Unlikely, due to "The Husbands of River Song" bringing closure to her and the Doctor's story, unless Series 10 is set within those 24 years. "The Return of Doctor Mysterio" formally Jossed this.
  • Clara's Gallifreyan echo from the opening of "The Name of the Doctor", regenerated into a new body since Jenna Coleman left at the end of Series 9.
    • Unlikely, due to the Doctor currently being an exile from Gallifrey once again — how would she reach him?
    • How do you think she'd reach him? She'd steal a TARDIS and run away — Bye!
  • The Master's/Missy's daughter (if a background character from "Hell Bent" turns out to be her).
    • No such character appeared.
  • Rigsy.
    • Very unlikely. Not only does he have a family, his last adventure with the Doctor and Clara ended with the latter dying in his stead, the former being delivered into the hands of enemies, and (in a Deleted Scene revealed in the shooting script) Rigsy was left to inform Clara's loved ones and colleagues of her death, etc. A filmed Deleted Scene confirms he was emotionally crushed by these events, so Survivor Guilt alone would make him a no-go as a companion, especially if the Doctor's memories of him were compromised by the mind wipe. And as the whole final stretch of Series 9 was about the Doctor finally learning to accept and move on from loss, the last thing he needs is a companion related to a gigantic one.
  • Psi and/or Saibra from "Time Heist".
  • Somehow related to Leela or her origins, as BBC Three reran "The Face of Evil" not long after the Christmas special aired on the main stem. BBC America ran "Genesis of the Daleks" just before the two-parter that opened Series 9 and brought back Davros; perhaps the BBC is laying groundwork. Perhaps it's her half-human, half-Time Lord offspring?
  • Journey Blue from "Into the Dalek". The Twelfth Doctor was not comfortable having a soldier as a companion and turned down her request, but that was very early in his tenure. Now that he better understands himself and the good qualities of those who choose to be soliders, perhaps they can learn from each other should their paths cross again?
  • Jossed . . . but also confirmed because there are two companions in this season! While Bill Potts — evidently a new character — was the first to be announced, the second one turned out to be Nardole, River Song's associate from "The Husbands of River Song".

The new companion will be played by a returning actor...
Continuing NuWho tradition in which every new companion is played by someone who already appeared on the show, sometimes in a different role:
  • Freema Agyeman appeared as a Torchwood 1 employee in "Doomsday".
  • Catherine Tate appeared as Donna in "The Runaway Bride".
  • Karen Gillian appeared as a soothsayer in "The Fires of Pompeii".
  • Arthur Darvill appeared as Rory throughout Season 5.
  • Jenna Coleman appeared as Oswin Oswald in "Asylum of the Daleks" (though, of course, Oswin was actually an echo of Clara).
  • Even Billie Piper conforms to this rule if you count her appearance as The Moment in "The Day of the Doctor", which from the Doctor's point of view chronologically precedes "Rose".

So whether playing a brand new or returning character, the new companion will be portrayed by someone who already has at least one Doctor Who episode to their credit.

  • Jossed, unless she's retroactively written into a past-Doctor story like Billie Piper, as Pearl Mackie has never appeared on the series before.

Steven Moffat has claimed the next companion will be an all-new character who will have a different relationship dynamic with the Doctor than his Platonic Life-Partners / Distaff Counterpart relationship with Clara. Possible occupations, identities, character traits, etc.:
  • Non-human — It would be a first for NuWho to have a companion of this type. It might be a robot, an alien...
    • Jossed with Bill — but Confirmed for the other companion for Series 10, Nardole, who was stated by Matt Lucas to be a Human Alien with "special abilities" in an interview.
  • A child — The Twelfth Doctor consistently gets on rather well with kids, and a child companion would bring out his protective side but not a tender, romantic one, which he had plenty of (for good and ill) with Clara and later River Song. Also, this is the likeliest option for those who want to see a solo male companion for a change yet won't serve as a potential turnoff to female viewers (see below).
    • A child on the TARDIS would bring several problems (not to mention more Alder backlash), mainly the issue that companions are constantly in danger; I don't think the Doctor would want to endanger little kids like that.
      • Who said anything about a little kid? The Doctor certainly had plenty of teenaged companions in the old days. Might be nice to have another 15-17 year old who could bring out the Doctor's fatherly side.
    • Jossed: Bill looks to continue the trend of young adult women as companions.
  • Someone older than 30 — If the Doctor doesn't want to travel with a kid, an older character interacting with him could make for an interesting new dynamic — one of near-equals in a different way than Clara-Eleven/Twelve's was. (Unfortunately, probably not likely because of Peter Capaldi's advancing age; executives want "youth appeal" and right now, that function falls on the companion.)
    • Jossed with Bill: Her actress, Pearl Mackie, turns 30 in 2017!
    • Confirmed with Matt Lucas, who's 43 and returns as Nardole.
  • Not from Earth of The Present Day — Think of the fresh eyes this would bring to the TARDIS and the Doctor's adventures, whether he/she was from the past or future!
    • Confirmed for secondary companion Nardole, who is from the far future.
    • Jossed for Bill — she's from the present day, all right. Which means her ignorance of the Daleks is now an entirely new question, given that she really ought to know what they are.
  • Differently-abled — For an interesting new avenue to interactions or adventures, how about someone who has a so-called "disability"? Deaf? Blind? Mute? Uses a wheelchair? Autistic? Or are these options unlikely because complaints of Reed Richards Is Useless might come up given the general setting and the Doctor's knowledge?
    • Jossed ... although the Doctor himself does spend a couple of episodes blind. Twelve does ask little person/scientist Erica what she's doing after the current emergency is resolved, as if considering inviting her along, but outside events intercede and it's not followed up upon.
  • An augmented/enhanced human — Because a companion with special abilities could hold their own better in dangerous situations, and leave Twelve feeling less pressured as to his "duty of care".
    • Confirmed with Nardole in the sense that he's an augmented Human Alien, although the extent of his abilities is unclear.
  • Physically aggressive — It's been a while since we had a really combat-oriented character like Leela or Jamie in the TARDIS, and having a hotheaded foil to rein in would give Capaldi lots of opportunities to complain about things! Speaking of Jamie...
  • Male — No solo male companion has appeared in NewWho as yet, and a guy would certainly bring a different dynamic to a relationship to the Doctor. The downside is that this would leave the show without a female regular, possibly turning off the show's significant female fanbase. (There likely will never be a solo male companion in the show unless the prospect of a female Doctor becomes a reality.)
    • These days, a Companion being male does not preclude the prospect of romance with the Doctor. See Jack Harkness.
    • An appealing enough male Companion might draw in more female viewers, as Jamie and his knees did.
    • Jossed with Bill, although she has a man's name. Confirmed with male secondary companion Nardole.
  • A relative of his — or of a companion — The Doctor has apparently had multiple children, even before Jenny, and at least one grandchild that we know of. Any one of them could have offspring, not to mention the possibility of the Doctor himself having siblings with offspring. There's also the option of a relative or descendant of someone he's traveled with previously.
  • Yet another pretty girl who falls in love with the Doctor — Because past history!
    • Jossed because she's gay; the ending of "The Pilot" even teases that her being reunited with poor Heather might figure into the year's Story Arc.
  • Non-Caucasian — While there have been many one-off and recurring non-Caucasian characters in NewWho all of the companions have been white with the exception of Mickey Smith in Series 2 (and being Rose Tyler's boyfriend had a lot to do with this) and Martha Jones in Series 3, both of whom were black. It's time to mix things up again — a new companion could be Hispanic, Middle Eastern, Indian, Far Eastern, etc.
    • Confirmed! Bill is a black woman.
  • Asexual
    • Unconfirmed. You can be both gay and asexual.
      • Jossed: Bill dates, and is at least implied to be interested in more than just a cup of tea when she invites a prospective girlfriend over.

The Doctor's next companion will be his and River's offspring
There was a hint in the Christmas special, when River said 'Hush, mummy and daddy are talking.' So either she had already had a child, or she and the Doctor were very busy for those 24 years on Darillium. That would create a companion just the right age for the younger audience.
  • The context of that line is River is speaking figuratively; no child required or implied.
  • There's another hint in the ending of "Forest of the Dead," when River's dream world within the library computer includes tucking in her three children for the night.
  • River has apparently run off with the TARDIS without the Doctor's knowledge many times before, so she might even have done so for nine months, or however long Time Lord gestation is, possibly even staying with their child(ren) or going back to visit regularly until they were grown, without the Doctor even knowing she'd been pregnant!
    • Why would she need to? I mean, they could certainly go on adventures (alone or together) during the 24-year-long night on Darillium. But they do have 24 Earth years (at least). They could easily have one or more children during that time, depending on just how Gallifreyan reproduction unfolds.
  • Jossed, unless neither parent ever told her what a Dalek is!

River Song will be the companion for Series 10
The nights on Darillium are 24 years long. Why not go on an adventure or two during that span? They already know they have all that time.
  • Jossed. "The Return of Doctor Mysterio" reveals that its action takes place not long after the Doctor left her for good and he is now struggling with melancholy and loneliness, setting the stage for Bill's arrival.

New companion Bill is Donna's daughter
Sass runs in the family. Just saying.
  • There are WMG's elsewhere that Bill is from the '80s, so that would rule her out as Donna's daughter. But it was this troper's first thought on seeing her. Maybe Donna met a Weeping Angel and ended up back in The '60s whilst pregnant?
  • With the Jossing of Bill being from a prior decade — rather she's from The Present Day, as Donna was — this looks increasingly unlikely. Moffat has admitted, however, that Bill is a companion in the tradition of Donna; she's sassy, more questioning of the Doctor and his world and not as natural a fit for them as Rose, Amy, and Clara were, etc.
  • Jossed. We see photos of Bill's mum in "The Pilot".

The new companion is transgender/transsexual, hence the name Bill.
It would be a very topical addition to the storyline. Plus if Bill is from the '80s, as some are suggesting, she will have met a lot more prejudice as the AIDS scaremongering was at its zenith back then. The Doctor will show her a more forgiving world.
  • It's been confirmed that Bill's not from the '80s, so this angle can't be explored.
  • Jossed: Bill is gay, but seems comfortably cis.

If Bill's not Asexual, her main love interest will be an Asian girl
A nice change from the straight, black+white relationships in the show. During Bill and Nardole's travels with the Twelfth and Thirteenth Doctors, they will meet a spunky Asian girl in her late twenties, that helps them in an adventure, and falls in love with Bill through it. Then Nardole goes away from the TARDIS to work in a restaurant on Darillium. A few episodes later, the Doctor and Bill meet the Asian girl again and have another adventure with her. Then the Doctor and Bill invite the Asian girl in the TARDIS. Bill and the Asian girl eventually leave together.
  • The confirmation that Bill is gay has made this theory a lot more plausible than I initially viewed it.
  • Jossed: The two women she expresses interest in are Heather, who is white, and Penny, who's black.

Nardole is an Adaptive Life Form
When we first meet Nardole, he's a Butt-Monkey and a bit cowardly, in the employ of River Song. When we meet him again, he's traveling with the Doctor, and is now quite the Deadpan Snarker to him. But in "The Return of Doctor Mysterio", he's quite supportive to Grant, there quickly with a bottle for Jennifer. He also takes a years-long detour in the TARDIS where he ruled 12th century Constantinople "firmly but wisely". Nardole may be a race of alien whose hat is being just what someone needs, personality-wise at least, right when they need it. Someone to verbally spar with the Doctor, to support River when she needed it, to be kind and caring to a nanny moonlighting as a superhero, and to be the wise ruler of an ancient civilization.
  • Matt Lucas did confirm in an interview that Nardole's a Human Alien . . .
  • Jossed: Word of God states that Nardole's change in behaviour is because he was employing Obfuscating Stupidity in "The Husbands of River Song".

Bill and Nardole will be one-season-and-done companions
The last time there was a Doctor and showrunner switchover, when David Tennant and Russell T. Davies left, the handover was a complete one, with Eleven starting fresh with new companions. With both Peter Capaldi and Steven Moffat leaving at once, it's likely that Bill and Nardole will be written out in either the Season Finale or Christmas Episode (possibly earlier in the case of Nardole) so Thirteen can get a fresh start with Chris Chibnall. Possible ways they might be written out:
  • Perhaps Twelve will have to regenerate when he saves one or both of their lives, which would be in the tradition of Five, Nine, and Ten's regenerations, and he and the TARDIS set things up so that they can move on to relatively ordinary lives.
  • The February 2017 teaser has Bill note that she loves traveling with the Doctor — "even if it kills [her]." Might she make the ultimate sacrifice in the end to leave a completely clean slate for Thirteen? Points working against this option: It would be a depressing ending to Twelve's story for him to lose another companion to the Grim Reaper right before he died — especially since it would have to be afforded at least as much emotional weight and plot significance as Clara's death to avoid more complaints that Clara was a Mary Sue More Special Than Anybody. And given four sets of revival-era companions managed death-cheating loopholes of some kind in their departure stories (Rose: alternate universe, Donna: memory wipe, Amy and Rory: lives lived out in the past, Clara: near-infinite adventures within her last moment of mortal life), it's more likely Bill will get one of her own if the show feints at killing her off.
  • "Thin Ice" and "Knock Knock" both drop some hints that suggest that Bill will at the very least stick around to witness the upcoming regeneration, meaning she might be around for the next season. But given that the Doctor looks to semi-regenerate in "The Lie of the Land", would that be sufficient for her?
  • The semi-regeneration was actually faked, so I doubt it.
  • Confirmed.

If Bill is a one-season companion, she'll choose to leave
The only previous New Series main companion who left completely on their own terms, of their own volition is Martha Jones. This is in sharp contrast to the classic series, where companions usually left on their own terms (the exceptions being Jamie, Zoe, Adric and Peri). It's about time we had another companion who got to depart on their own terms, instead of getting a Dramatic Departure. (Of course, if Bill at any point expresses the intent to travel with the Doctor for the rest of her life, than she's just signed her own Dramatic Departure Warrant.)
  • With the ending of "The Pilot" suggesting she hopes to be reunited with Heather at some point, should that turn out to happen it would be a strong motivation for her to leave of her own volition.
  • Partially confirmed.

Bill is Orson Pink's great-grandmother.
In "Listen", Clara met Orson Pink, a time-travel pioneer from the 22nd century who — due to his appearance, last name, and ownership of the little "soldier man" young Danny had — she (and the audience at the time) assumed to be a descendant of her Love Interest Danny. His mentions of time-travel related weirdness around one of his great-grandparents (the reason he volunteered for the time-travel project to begin with) leads Clara to naturally assume he's her and Danny's descendant. Then in "Dark Water" Danny died (and for that matter Clara never became a mother before her death — it's unlikely, in her time-looped state, she can have one via wiggle room). Moffat later confirmed that Orson was a lateral descendant. However, that still leaves Orson's mention of one of his great-grandparents possibly being a time traveller. Maybe it was/will be Bill? If nothing else, this would be an interesting parallel to the Ponds turning out to be River Song's parents during Eleven's tenure.
  • Looking unlikely, given what happens to her in "The Doctor Falls".

Bill was brought forward in time.
Her intro short, "Friend from the Future", and by extension "The Pilot", the season premiere, show that she is totally ignorant of the Daleks. As pointed out above, if she was from about 2010 or later, she would definitely know what a Dalek is, because she would have lived through the events of "The Stolen Earth"/"Journey's End", which was, in case anyone forgot, a massive Dalek invasion in which, among other things, they physically relocated the Earth. However, the March 13 and April 3 trailers include a shot of the Doctor and Bill meeting one of the emojibots from "Smile", and Bill's line in this clip ("They speak emoji!") makes it perfectly clear she is familiar with the meaning of the word — a word that didn't really come into use in the English language until around 2013-2014. Finally, "Friend from the Future" has a line where the Doctor describes 2017 as "the future" (which it was when the short was released), suggesting that, to Bill, the year 2017 is the future. A possible answer to this? Bill is from somewhen before 2010, and was somehow — possibly in a way similar to classic series companion Ace — brought forward in time to 2014 or 2015. It's also possible that the process itself, or whoever was responsible, scrambled her head somehow so she doesn't realize it's even happened until she meets the Doctor.
  • Jossed.

Nardole is Dorium Maldovar.
Nardole has mentioned he swapped his face while on the run and used to be blue. He also has a criminal past. Dorium's home era was some time in the 52nd century, and he's somewhat unscrupulous. Maybe they're the same guy? Nardole's age when the monks invade is 237, which could work as an age for Dorium so long as he's not too old when we first seem him(assuming The Slow Path, 5145 to 5343 would still allow Dorium to be 39 tops when first seen, and even then this is a universe with time travel). And would it be that hard for Dorium to have his head transplanted on a new body once he gets bored of not having one? Wanting to move away from his old life Dorium went under a new identity and through his life of crime underwent a number of plastic and vocal surgeries to become Nardole. He still gets along with the Doctor, but would rather not mention their past when he was Dorium. Yes, I know 12 meets Dorium in the comics, but even if they are treated as canon this could just be an out of order adventure, which would give Nardole more reason to not reveal his past.

    The Twelfth Doctor's Regeneration 
When Peter Capaldi regenerates, Clara will return for a cameo.
Because when 9, 10, and 11 regenerated, the first face they saw was the same as the last. (Not counting Ood Sigma for 10.)
  • Or a Clara will return. There's still several million of her out there, after all.
  • The ending of "Hell Bent" revealed that the Doctor can no longer remember what Clara looks like or recognize her on sight, so in order for her to appear again, one of the following options will have to happen:
    • She'll appear in the flesh for some reason, and a miracle will cause him to regain his memories just in time. Perhaps The Power of Love?
    • He will suddenly recover his lost memories just before he regenerates (perhaps the energy gives his brain a push?) and have a vision of her, ala Amy appearing to Eleven.
    • He won't actually remember, but will deduce Clara's identity.
  • Alternatively, she'll have a major role in the regeneration story when it comes, possibly connected to a larger Story Arc/Myth Arc the way Rose wound up key to that of Series 4 (see below for arc ideas).
  • Confirmed: Clara makes a brief appearance restoring the Doctor's memories. However, she is not the last person he sees.

Twelve will regenerate in the 2016 Christmas Special, and Series 10 will introduce the Thirteenth Doctor...
Doctor Who's same-day ratings aren't what they used to be, and Twelve hasn't been as popular with mainstream audiences as Ten and Eleven were. Perhaps with the longer-than-usual delay between seasons he'll end up having an abbreviated tenure and the "event television" aspect of Series 10 will come with the introduction of Thirteen... or...
  • Jossed: Series 10 is all about Twelve.

Series 10 will end with Twelve regenerating
As Steven Moffat is leaving after Series 10, it would follow the precedent of Russell T. Davies / David Tennant for Peter Capaldi and the Twelfth Doctor to leave with him. The BBC's press release saying that the delay to Spring 2017 will allow it to be positioned as event television would suggest that some huge events are in store, and a story culminating in a regeneration is about as big as Who gets in a regular season. As well, this would give Twelve three seasons' worth of stories, following in the footsteps of Ten (three-and-a-half) and Eleven (three), and even before the announcement of Moffat's departure Capaldi had noted in an interview that he was considering leaving after Series 10 to do other work.
  • I theorised last time a regeneration was coming up that 11 would regenerate sacrificing himself. Mayhaps 12 will regenerate that way.
  • Jossed. Not only did Capaldi go on record to say he was asked to stay for Series 11, all signs point to Twelve appearing in the 2017 Christmas episode, and thus he cannot regenerate at the end of Series 10. So does that mean...

Twelve will regenerate in the 2017 Christmas Special
If he stays for Series 10, then he might follow the example of Ten and Eleven and regenerate in the post-season Christmas special rather than the Season Finale.
  • This was initially confirmed by Peter Capaldi on January 31, 2017. This was doubtful for quite a while, with Steven Moffat saying he wasn't expecting to write a regeneration story as his final script back in 2016, but Capaldi is leaving with this episode, making Series 10 the Twelfth Doctor's final season. But as of the final Series 10 trailer on April 3, which ends with a shot of Twelve clutching his stomach and staring at his own hand, which is awash in regeneration-energy, it's being played with. Could be that his regeneration starts in the Season Finale, but is time-delayed in some way (a la the Sisters of Karn keeping Eight alive) to allow him to engage in one last story. Or perhaps the 2017 Special will take place in flashbacks and/or inside the Doctor's own head, as he's regenerating? Twelve's run has had a lot of references to Ten's run. Given that Ten held his regeneration off for several days by force of will alone, perhaps that's what happens. More theories on this are listed below.

Since Capaldi leaves in the 2017 Christmas episode, the new Doctor will be — Your Guesses Here!
  • Peter Dinklage
    • Unlikely because no matter how good he is at doing a British accent, the world will end before the BBC casts an American as the Doctor. There would be riots in the streets. The Queen would tut in disapproval.
  • Sophie Okonedo — For the same reason as Colin Salmon above, but also encompassing the Doctor's wish to remind himself of the people he should help. Also, she'd be the first female Doctor and she would be utterly fantastic, just as she was as Liz 10. "I'm the bloody Doctor, mate."
  • Colin Salmon — Breaking tradition by being our first Doctor of colour, and continuing the tradition of being someone who's previously appeared on the show.
    • We've also seem him back in "Silence of the Library" and "Forest of the Dead" as Dr. Moon — a mysterious, benevolent-but-ominous-at-first figure who even helped someone Dare to Be Badass. You couldn't have a better audition for playing the Doctor, and he did a good job!
  • Maisie WilliamsGame of Thrones must be coming to an end soon, and she's not only female, but very relevant at the moment. It would also fit in with the Doctor's idea of choosing faces that make him remember the people he has helped, or failed to help. He made a big mistake with Ashildr that he won't want to make again. Alternatively, he doesn't see it as a mistake per se but a reminder that sometimes No Good Deed Goes Unpunished (especially one involving a Sadistic Choice in the heat of the moment!) and one must live with its consequences, good or ill.
  • There is no way in Hell that the BBC is going to cast someone who's already appeared on the show as Thirteen, not with the fact that Capaldi was Recast as a Regular. They are not going to do Recast as a Regular twice in a row. Maybe with Eighteen, in the future, but not Thirteen.
  • Sacha Dhawan
  • Rupert Grint
    • Then he'd finally be ginger!
  • Chiwetel Ejiofor
  • If he became Peter Capaldi because the events of "The Fires of Pompeii" reminded him to always save whoever he can even if it's against the rules, then since 12 questioned whether or not he was the good guy often, it might lead to him regenerating into Richard E. Grant, the face most commonly worn by the Great Intelligence. A sneaky reference will make the events of "Scream of the Shalka" canon and we'll even get a wink to "The Curse of Fatal Death".
  • Jamie Campbell-Bower
  • Right now, the three names that appear to be the favorites are Kris Marshall, Phoebe Waller-Bridge, and Tom Rosenthal.
  • All Jossed. It's Jodie Whittaker.

In 12's final story he will revisit the Paternoster Gang
  • Book Ends?
    • There are a few problems with this: 1) The story will probably involve Gallifrey and/or the Time Lords, as Ten and Eleven's finales did, and it would be hard to work the gang into that setting. 2) He hasn't seen them since he was traveling with Clara, so they would wonder where she is, which would make conversation really uncomfortable. 3) It will have been 3+ years since "Deep Breath" aired, and the gang was more a part of Eleven's tenure than Twelve's. However, if a "Journey's End" or "The End of Time"-style denouement is in the cards for Twelve's finale, there's a good chance they could be worked into it in passing at least, especially if Clara makes some kind of appearance.
  • Jossed.

The regeneration will create the Valeyard.
Perhaps whatever causes the Doctor's regeneration will also create the Valeyard, as a Sequel Hook for Series 11. And it could be that, at the time, only the audience knows that this has happened, and the Doctor doesn't find out until late in Series 11.
  • Looking jossed for the time being.

The regeneration will be very explosive and cause damage to the vicinity.
After all, both of his past two regenerations were.
  • Very much confirmed: the regeneration causes the TARDIS to be so badly damaged that she winds up throwing the Doctor out at 30,000 feet.

Whoever's cast as Thirteen will have a name connected to the number.
After all, so far in the new series we've had:
  • Nine: Christopher Eccleston — 9 letters
  • Ten: David Tennant
  • Eleven: Matt Smith, eleventh person by that name on IMDB
  • Twelve: Peter Capaldi, 12 letters... The trend is clear.

Regarding the last shot of the April 3 trailer . . .
The Doctor is seen bent over, one hand to his stomach and the other glowing with regeneration energy. What's going on here? Well, assuming it's not a fakeout, the Doctor gets the injury that will cause him to regenerate in the first half of the Series 10 finale, and then is forced by circumstances to hold it off until near the end of the Christmas special. This also means that the finale will end on a cliffhanger that leads directly into the Christmas special, which takes place immediately afterwards. This would be especially interesting because it would be a whole new way to tackle a regeneration story.
  • Alternately, he'll be mortally wounded and commence regenerating at the normal pace, but the Christmas special will reveal what's going on in his head during the process. "Heaven Sent" showed us how the Doctor's Mental World works when he's in the midst of a life-or-death crisis; the holiday episode could revisit that concept, by showing how he finds closure for his persona as Twelve and unpacks new facets of personality and mannerisms that will be emergent in Thirteen. It'd make a great capstone for Capaldi's tenure as one of the most dramatically-oriented Doctors, and would add one final Twelve/Clara parallel to his story: living out one last great adventure that's suspended between one heartsbeat and the next.
    • That seems like an awfully low-key Christmas Episode and Grand Finale for a Doctor, though. Doesn't Twelve deserve to go out with a bang as his predecessors did?
    • Just because it's in his mind doesn't mean it has to be "low-key". The Doctor's got some pretty dark things in his head too, remember, and it could be that defeating them in his Mental World - which wouldn't have to be just the TARDIS this time - could be necessary to suppress that part of himself in Thirteen. If he wins, his new regeneration can then emerge in time to avert the threat that killed Twelve, but if he loses... hello, Valeyard!
  • Jossed: It's from "The Lie of the Land", and a fakeout.

Alternatively, the regeneration seen in the April 3 trailer is a fakeout.
He could possibly use some of the energy to heal himself, and then transfer the remaining energy into something else. It's not the first time he's done that.
  • The Doctor was able to do that back in "The Stolen Earth"/"Journey's End" because he had a receptacle in the form of his severed hand from "The Christmas Invasion". If this is what's going on, he would have to have a similar kind of receptacle. Also, the staved-off regeneration back in Series 4 was not particularly well-received by the audience.
  • Alternatively, it could be transferred into someone else. Regeneration energy (albeit all of River's remaining regenerations) saved Eleven from Judas poison in "Let's Kill Hitler", and Twelve's energy revitalized Davros and all of the Daleks on Skaro in "The Witch's Familiar". While it apparently cannot bring someone back from the grave (otherwise he'd have used it on Ashildr/Me and/or Clara Oswald), it can keep a wounded person from getting to that point. Perhaps someone near and dear to him will be saved in this manner? Especially since it still hasn't been clarified how many regenerations the Doctor was granted by the Time Lords in "The Time of the Doctor".
  • And what if regeneration energy could be summoned or taken by something or someone else? Could an enemy be trying to steal it from him?
  • Also supporting the possibility that this is a fakeout:
    • Due to prior precedent, it would be a mean slight against the Twelfth Doctor, Peter Capaldi, and their fans to not make the Christmas special Twelve's Grand Finale. If Ten and Eleven were seen out that way, Twelve has to as well, especially since he isn't getting a "bonus" special or two beforehand as they did. (Unless Moffat and co. are really hiding something.)
    • Steven Moffat is writing the Christmas Episode. Why would he write the debut story for the first Chris Chibnall-era Doctor as his final Who script?
  • Also, who's to say that the scene doesn't happen earlier in the season? Blogtor Who pointed out that the shot has him in the coat he's known to be wearing in Episode 8, "The Lie of the Land". And since then, Moffat's Radio Times synopsis of that episode — the conclusion of the "Monks"/Prophets of Truth storyline — says that Bill is faced with the possibility of having to kill the Doctor, because he's a victim of a mass delusion that doesn't affect her at the time. Perhaps with a little technobabble Twelve could give Ten a run for his money in delaying a regeneration!
    • Just because he's confirmed to be wearing that coat in "The Lie of the Land" doesn't mean he's not going to wear it again.
    • "The Lie of the Land" involves a mass delusion affecting everyone but Bill. Including the Doctor. It's possible that the clip could be from there, depending on what exactly the delusion is.
    • Further details picked up from trailers and official stills from "The Lie of the Land" led the Radio Times to theorize that yes, it is the episode with the regeneration-or-is-it? scene. A figurine of a Monk is on the desk, he wears the same coat — the shabby one that first appeared, interestingly, in the Missy flashback scenes of "Extremis" — in the stills, he's surrounded by black-suited men with the Monks' "Truth" insignia on their's all adding up.
    • Breaking a delusion to help save humanity — not just his own delusion, but others' — might be just the thing to apply regeneration energy to. Oh — and he's still blind in "The Lie of the Land". Wouldn't it be a nice side effect of him giving up a life or two to at least get his sight back? Wonderfully metaphorical too — he would see literally and figuratively again!
  • Confirmed, but not in the details: The Doctor fakes a regeneration as part of a Secret Test of Character in order to confirm that Bill wasn't under the control of the Monks.

"I might regenerate... I don't know... Feels different this time..."
This is essentially just elaborating on the first WMG to address the April 3 trailer. Since then, Capaldi said in an NY Times interview that his regeneration is not as "straightforward" as the previous several (if you can call a 13th regeneration that levels a town "straightforward", but I digress), and that this isn't "the same process he's gone through every time." Maybe the Doctor will be critically injured in either "World Enough and Time" or "The Doctor Falls", but the injury will somehow disrupt his ability to regenerate (a specific kind of radiation, or some other bit of technobabble), leaving him in a state of flux, until he finally regenerates in the 2017 Christmas special. The dramatic possibilities that could come of this idea are quite juicy: maybe the Doctor will experience "regeneration seizures" of some sort, with a regeneration that abruptly starts and stops in random spurts, and maybe this is what we're seeing in the April 3rd and 15th trailers (The April 15th trailer in particular makes it seem like he's very suddenly and unexpectedly beginning to regenerate). Maybe one of these seizures will come at the worst possible moment for the Doctor to up the tension. Maybe we'll see flashes of the next Doctor's fledgling personality or appearance (like an eye color change, or a brief lapsing into the next actor's voice). Maybe the Doctor himself will be unsure of whether or not he can regenerate again after the injury, or even if he can, what he will regenerate into. Maybe we'll see the Watcher again, or at least a similar kind of concept. In short: this regeneration will be less The Nth Doctor, and more Game-Breaking Injury or Body Horror.
  • With the Doctor blind as of "Oxygen", growing more and more infirm over the remainder of Series 10 is a possibility, and Reasons will be given as to why he cannot regenerate yet. In that case he'll finally find his "rest" in the Christmas Special.
    • That part is jossed, as his blindness is cured by Bill making a Deal with the Devil in "The Pyramid at the End of the World".

The regeneration episode, if it's the 2017 Christmas special, will have the word "Time" in the title.
Both of the Christmas specials that have been regeneration episodes, "The End of Time" and "The Time of the Doctor", have that word in their titles. Given that there's already been a tradition established of the word "Christmas" only appearing in the titles of a particular Doctor's first Christmas special, it looks like there could be a trend developing of, if a particular Doctor's last episode is a Christmas special, having "Time" in the title.
  • But then why is the penultimate episode of Series 10 already called "World Enough and Time"?
    • Ah, well, when this theory was initially posted the title of the penultimate episode hadn't been revealed yet. Possibly, tying in with a theory above, that episode is when he receives the injury that causes him to regenerate.
    • Capaldi has gone on record as saying that Twelve's regeneration will be different than Ten and Eleven's were, so perhaps it indeed will be spread over several episodes (i.e., he won't/can't regenerate right away because of the current crisis with the Cybermen)? Then the Christmas episode could use "Time" in the title too, if that convention were to still be followed.
    • Interesting tidbit: Eleven once used regeneration as a threat, when he was nearly converted into a Cyber-Planner in "Nightmare in Silver". He warned "Mr. Clever" that he could trigger the process to expel all the cybernetic implants that'd been forced upon him. In hindsight, we know this was a bluff — Eleven couldn't regenerate until "The Time of the Doctor" rebooted his cycle — but perhaps Twelve will actually need to go through with it.
  • Confirmed. The title is "Twice Upon a Time".

The regeneration story will involve the Time Lords and Gallifrey
Another thing suggesting Twelve's regeneration won't go through until the Christmas Episode is that Ten and Eleven's grand finales both had the Time Lords central to their plots, though they stayed offscreen in Eleven's case. On top of that, "Hell Bent" ended with a lot of loose ends regarding the Twelfth Doctor's relationship with his people and birth planet (Is he a wanted man for trying to save Clara, or do they forgive him due to the circumstances? Who's Lord President now? and so on), none of which look to be addressed in Series 10 given the announced episode synopses and the fact that the Time Lords and Gallifrey were established to be in hiding even after leaving the pocket universe and probably wouldn't interfere in even a Cybermen crisis. Moreover, many fans are still sore that "Hell Bent" didn't focus on Gallifrey. Between this and the Daleks apparently only getting one go-round in Series 10 in "The Pilot" (and not even as the mainantagonists!) it's possible that it's all being saved for the regeneration story. And if the regeneration is to be an atypical one, they might or might not have something to do with why it is.
  • Looking doubtful as no trailer or synopsis as of November 2017 mentions them.
  • Jossed.

What appears to be regeneration in the trailer wasn't naturally triggered
The Doctor appears to have guns pointed at him in the trailer, but there's no visible indication that he'd sustained any shots or other fatal injuries that might have naturally triggered the regeneration process. There's a possibility that whatever's happening may be forced, either by the Doctor himself — as Time Lords have been shown to be able to do — or someone else entirely. If it's an attempt by someone else, it may fail, or it could be a deliberate attempt at a fakeout by the Doctor.
  • With the development in "Oxygen" that the Doctor is currently incurably blind, it's possible that he has to force this on himself to regain his sight. He doesn't do it sooner because...Reasons yet to be revealed.
    • Jossed.
  • The Next Time trailer for "The Lie of the Land" ends with Bill shooting the Brainwashed and Crazy Doctor in the chest to save the world because he is the "link" between humanity and the Monks and must die to stop the latter. How he manages to regenerate without changing his physical form is yet to be revealed.
  • Confirmed: It was actually a fakeout by the Doctor as part of a Secret Test of Character in order to check if Bill was under the Monks' control. He was actually pretending to be brainwashed.

The Twelfth Doctor's last words?
  • "Fuckity bye!"
  • "Clara?"
  • "It's a shame, I rather liked these kidneys."
  • "Hope I'm ginger!"
  • "Maybe the eyebrows will be less aggressive this time!"
  • "I'm sorry."
  • "No!" If what was shown in "World Enough and Time" wasn't a fake out
  • "Where there's life, there's hope." (What the Third Doctor tried to say before he died, tying in with "Where there's tears, there's hope." Capaldi also grew up watching Jon Pertwee's tenure, so a farewell nod to his Doctor would be most appropriate.)
  • "All things end. But the end is where we start from." (Eleven's sad musing in his last story and the last line of Torchwood Season 2, which Chris Chibnall worked on, a symbolic cross between Moffat and Chibnall's works and the transition of one going out and the other coming in as showrunner.)
  • "Shut up."
  • All Jossed, they were: "Doctor, I let you go."

The Thirteenth Doctor will be female
Simply because Bill is gay and New Who can't help but ship the Doctor with his companions. To do it with this companion though, they'd need to turn the Doctor into a woman. Possibly she'll be subconsciously influenced by Clara, like having her accent the way Ten had Rose's and Twelve had Amy's (Rose and Amy having been the most significant people to Nine and Eleven respectively the way Clara was to Twelve), which could also invite Les Yay meta readings that may please Doctor/Clara shippers. Cue next series brimming with Ship Tease for a Missy/Doctor/Bill lesbian Love Triangle and the Internet exploding. Neat, looking forward to it.
  • Confirmed that the 13th Doctor will be female (Jodie Whittaker). Jossed that it will be for purposes of Les Yay Ship Tease, as both Bill (with her already-established lover Heather) and Missy left at the end of Season 10. (Bill is returning for the Christmas special but not been confirmed for Series 11.)

Possible titles for the Twelfth Doctor's Grand Finale
  • "The Twilight of the Doctor" or "The Dawn of the Doctor" — To call back to the titles of the final Eleven-era episodes and Eight's short
  • "No More" — To go with "The Doctor Falls", the Series 10 finale
  • "Heaven-bound" or "Heaven's Gate" — This would give each of Twelve's three seasons an episode title with Heaven in it
  • "The Promised Land"
  • "The Homecoming" — Especially if it involves Gallifrey
  • "The Day He Came Back" — If it involves Susan
  • "The Hearts of the Doctor"
    • Jossed. It's "The Doctors".
      • Also Jossed. That was the working title. It's "Twice Upon a Time".

The Doctor's apparent partial regeneration in "The Lie of the Land" will have a connection to his upcoming real regeneration
Okay, so in "The Lie of the Land", the Doctor will be shot by Bill in order to free humanity from the Monks' control, and it seems he's going to partially regenerate as a result, but doesn't do a full regeneration probably because of Missy. However, this will have unforeseen consequences that feed into his proper regeneration in the Christmas special. Perhaps, even, the regeneration is aborted because it's paused somehow, and the events of the season finale and/or Christmas special lead to it getting unpaused, this time with no way to stop it.

The next season's Story Arc will involve one or more of the following:
  • Rassilon and his High Council seeking Revenge upon the Doctor for deposing them in "Hell Bent".
    • Possibly Jossed. The 2016 Doctor Who (Titan) comic miniseries Supremacy of the Cybermen uses Rassilon's exile as its starting point (he teams up with the last Cybermen, they become able to time travel, chaos ensues). If the television show were going to do anything with Rassilon, they would probably issue an Executive Veto on Expanded Universe works doing anything with him, as happened when the 2015 novel Big Bang Generation had to be rewritten to substitute Benny Summerfield for River Song because its events would have contradicted "The Husbands of River Song". Possibly because Supremacy has a Reset Button ending and so it doesn't rule out future appearances for Rassilon.
  • Alternatively or simultaneously, the current Time Lord government trying to capture the Doctor for what he did to save Clara, not to mention abdicating his Lord President post!
    • Or, as a touching alternative, the Time Lords trying to make amends with the Doctor over the events of the Series 9 finale, much to his surprise — he thinks they think This Is Unforgivable! but in fact they love him too much for all the good he's done to write him off completely, and realize the wrongs that were done to him.
  • The Minister of War mentioned in passing in "Before the Flood". Bonus points if it turns out to be a previously-established villain (Rassilon, Davros, Missy, etc.).
    • Triple bonus points if it turns out to be the War Chief, who was shot before regeneration was an established feature of Time Lords and could therefore still be around.
  • Missy, whose return is confirmed in episode six ("Extremis"), executing a new scheme:
    • A collaboration with the Daleks.
      • Jossed. Between the three-parter dealing with the Prophets of Truth and the two-part Season Finale once again having her and the Cybermen involved, AND Saxon!Master turning up at some point, there's just no room for a Missy-Dalek teamup within Series 10, though it's still possible for Twelve's Grand Finale until confirmed otherwise. Although some of the location shooting for the three-parter involves the same locales used for Skaro and Gallifrey exteriors in Series 9...
    • A takeover of Gallifrey, since the Doctor fleeing left a power vacuum at the top of its government.
    • Upon finding out what happened to the Doctor and Clara's relationship, trying to reunite them and rekindle their love in hopes of it causing more problems.
    • Apparently, she'll be scheming with her previous incarnation — yes, that's right, John Simm is back. I am not making this up.
  • A villain from the classic series who hasn't yet appeared in the revival serving as the Big Bad. Candidates include:
    • The Valeyard — One of the most requested vintage villains, yet virtually a non-person in NewWho save for a passing mention in "The Name of the Doctor", and he has next-to-no Expanded Universe appearances. Perhaps Series 10 will finally see the embodiment of the Doctor's dark side arrive? On the other hand, given that Twelve is not only a darker Doctor than most but also temporarily became a Woobie, Destroyer of Worlds in Series 9, the show might wait until a Lighter and Softer / Younger and Hipper Doctor comes along to bring out the "evil Doctor" as an antagonist.
    • The Rani — Another frequent request — with Series 8, there were fans disappointed to learn Missy wasn't her. Again, she hasn't seen many Expanded Universe gigs, having only been introduced to the Big Finish audios. On the other hand, are her For Science! ambitions too modest for a Big Bad? And with Gallifrey still in hiding, how realistic would it be for more than just the Doctor and Missy to be bopping around the space-time continuum?
    • The Black Guardian — The White and Black Guardians haven't been seen in-show since Season 20 of the original run, and, again, seem underused in the Expanded Universe. It's odd that the closest analogues the Whoniverse has to God and Satan never seem interested in its goings-on...
      • Or maybe it'll be a different pair of Guardians that will appear, that came into existence to watch over the Big Bang II universe.
  • An all-new Time Lord antagonist, possibly one who's well-meaning but causing trouble inadvertently rather than an outright villain for a change. They could be:
    • Trying to prevent the Time War from reigniting (i.e., keeping the Daleks from learning Gallifrey's location and/or that the Time Lords have returned) — or even trying to prevent it from beginning.
    • Picking up the pieces left by the Doctor exiling Rassilon and his cronies and then abandoning his Lord President post...and not doing a great job of it.
    • Trying to help the Doctor in some way, owing to awareness of trouble coming for him — could it be Rassilon? Other Time Lords? Missy? Another threat altogether?
    • Engaging in stealth operations against the Daleks in vengeance for the Time War, which runs the risk of giving away Gallifrey's hiding place and kicking off another one if the Daleks catch on.
  • The return of the unseen Gus from "Mummy on the Orient Express". Bonus points if, again, he turns out to be another previously-established character. Or might he be the Minister of War?
  • Circumstances that recross the Doctor's path with that of Clara. (Note: Maisie Williams said in February 2016 she was not returning to the show, so unless that changes, the following do not assume Ashildr/Me's presence.)
    • The Time Lords managing to track one TARDIS down, and the other swooping in to save it.
    • Clara making a Face–Heel Turn, due to being a functional immortal and growing detached from mortals just as the Doctor feared would happen if he made Me a companion; now the Doctor must bring her back to right...or, alas, destroy her. She could be the season's Big Bad.
    • A new or old Big Bad threatening the universe, perhaps resulting in many past characters banding together to fight it.
  • The Doctor's original family. Isn't it time we saw them — or at least a return appearance from Susan?
  • Characters the Doctor has aided over the years finally paying their debts to him by helping him in various ways. Especially after all his suffering in Series 9, in which the universe failed to prove You Are Not Alone, it's time everybody proved they love him the way River Song told Eleven they did.
  • Answers to one or more of the following still-unanswered questions:
    • How did the Master survive the events of "The End of Time"/"The Day of the Doctor" and regenerate into Missy?
      • Looking more likely with the reveal that Saxon!Master and Missy are teaming up!
    • When, where, and how does the Twelfth Doctor participate in the climax of "The Day of the Doctor"? And why, beyond the obvious Stable Time Loop answer — especially if he was contacted after the events of "Hell Bent"?
    • Who is the Hybrid of the Matrix's prophecy, and what is its role in the fate of the universe? "Hell Bent" suggested several possibilities, in particular the Doctor and Clara in tandem, but didn't confirm any of them, so there's still The Reveal to be made.
      • Jossed as of Doctor Who Magazine 504, as Steven Moffat confirmed the Hybrid was/is the Doctor and Clara. Unless Clara makes a surprise return at the end of Series 10/the Christmas show and/or the Doctor gets his memories back, which are possible now that it's been confirmed that this is the Twelfth Doctor's final season, this plot thread is currently a non-issue.
    • How many lives does the Doctor have left? Neither the Time Lords or the Doctor himself know.
    • The Doctor said in "Heaven Sent" that he left Gallifrey because he was scared rather than bored (his usual explanation). What was/is he scared of?
  • "The Pilot" has revealed there is SOMETHING in the mysterious vault at the campus the Doctor is teaching at, he has been trying to hold himself to being around it (with Nardole's help) for 50+ years, and he made a promise to SOMEONE that not only seems to forbid taking on a new companion, but necessitates mind-wiping Bill... though he chooses not to do so on both counts. What could be such a big deal that the Doctor would be trying to deny his wanderlust and need for companionship? Turns out... it's Missy!

The Daleks will return to the Big Bad role
During the Moffat era, the Daleks have largely been in the background rebuilding their forces after being reduced to near-extinction, from their renewal in "Victory of the Daleks" to the restoration of Skaro itself in the Series 9 kickoff. After dealing with the cleanup on Skaro, they could be nearing the point of consolidating their forces into another attack, possibly in pursuit of Gallifrey itself and threatening to reignite the Time War all over again.
  • The new-companion teaser clip features Daleks, so their return is Confirmed. Whether they'll be the Big Bad or just a one-off has yet to be revealed, but as this is their last chance to be the former in Twelve's tenure, either over the course of a Story Arc or in the Christmas Episode, it's looking more likely.
  • There's also the possibility that the Doctor's regeneration energy gave them and Davros some kind of "boost" when all was said and done — one that was teased in the 2017 Annual, of all places.
    • Jossed. The two-part Season Finale involves Missy and Cybermen once more, the Mondasian Cybermen (the latter making their first appearance since "The Tenth Planet") in particular. The Daleks instead are secondary antagonists of "The Pilot", the season premiere. Unless they pull a surprise cliffhanger ala "Army of Ghosts" the Daleks might have to wait until the Christmas Episode to make their big move.

Series 10 ending ideas
  • The question of Clara: Clara's death is a fixed point in time, that much is established. Ashildr has talked about having infinite life, but finite memory, and my guess is the same will happen to Clara. The situation becomes that both Clara and Ashildr forget that Clara must at some point return to Gallifrey to die, at which point the shit hits the fan. With the neural block in place, the Doctor has no idea what Clara looks like or what to look for, so it's up to The Doctor and the new companion to assemble the puzzle and find Clara and Ashildr (who may have been conveniently separated), and convince Clara, who at this point has lost her mind a bit due to the "finite memory, infinite life" situation, to sacrifice herself and save the universe from the denial of a fixed point. At this point, or soon after, the Doctor regenerates for a reason I haven't come up with (I hope not, Capaldi is my favourite Doctor - but last time we got a new showrunner, we got a new Doctor), neural block is gone, 13 is ready to travel on with his/her memories intact.
    • Working against both this — and other Clara-related storylines — is Bill's presence. One of the most common complaints about Clara was that she was a Mary Sue whose story overtook the Doctor's over the course of her tenure, who always got all the breaks culminating in her becoming a Distaff Counterpart. If she were to play a major role in Series 10, it would come at the expense of Bill's story, turning into something of a replay of Martha's arc in Series 3 (and given that both she and Bill are black...). If Bill really is to be one-season-and-done, she has to be a proper Deuteragonist to Twelve to have a satisfying character arc, so Clara can't be central to it.
  • Happy ending for Twelve: Twelve's previous series finales, "Death in Heaven" and "Hell Bent", were Downer Endings for him on a personal level. He and Clara parted over mutual lies in the former, and he was left without a companion — or even key memories — on top of being a fugitive from his home planet again in the latter. He also hasn't had a chance to get the credit and reward for saving the entire universe yet. Danny gets most of the credit in "Death in Heaven", though it was the Doctor who threw him the bracelet and solved an otherwise unwinnable situation. And few acknowledge his choice to give up his Tragic Dream in "Hell Bent" is heroic: it took courage and kindness to give up someone he loved for the greater good, return to his best self, and accept the consequences of the mind wipe, after suffering so long. While the followup Christmas Episodes for both seasons were upbeat (a reunion with Clara, a Happily Ever After with River Song), it would be nice to have a happy Season Finale for him — especially since the Christmas Episode afterward is his Grand Finale, which following series tradition would be a more melancholy tale. Something gloriously happy, ala the ending of Series 5:
    • He mends his fences with the Time Lords.
    • He is happily reunited with Clara thanks to the miraculous restoration of his memories and a Time Skip similar to that of "The Husbands of River Song" ensues, ending with her returning to her death.
    • He's ready to make a Heroic Sacrifice but the universe pulls together to prove it loves him.
    • He is finally reunited with his original family- or some at least.
    • He defeats an old, persistent enemy for good — no Joker Immunity this time!
    • He comes to terms with, if not defeats for good, Missy. As she's probably not appearing until the latter stretch of the season, there's a good chance she'll turn out to be the Big Bad again. The Series 10 finale could resolve this particular plot thread before giving him a bigger fish to fry in his Grand Finale.
      • Missy has since been confirmed as appearing in a mid-season three-parter as well as the two-part finale, so she will likely be central to the Story Arc (five episodes out of twelve is a lot for a recurring villain), and even Saxon!Master is part of the action this time!
  • Multi-Doctor crossover story: Aside from his "Day of the Doctor" cameo, Twelve hasn't participated in a televised multi-Doctor story while Ten encountered Five and Eleven collaborated with War and Ten. It would make for both a spectacular Season Finale and a lead-in to Twelve's Grand Finale. (It's doubtful the show would make Twelve's last bow a multi-Doctor story because he couldn't be the center of attention in that.)
    • Not necessarily something they'd need to cram into Season 10 just so Capaldi can claim multi-Doctor episode cred, however: it's entirely possible that Peter will bring Twelve back for the 60th anniversary special, alongside one or more successors.
    • Unlikely: Series 10 is going with a multi-Master storyline!
      • May be extremely likely because based on rumors that have been flying around, the 2017 Christmas Special will have David Bradley (Who played William Hartnell in An Adventure In Space and Time) playing the First Doctor, and that it may revolve around them saving Gallifrey as seen back in "The Day of the Doctor".
      • Confirmed. David Bradley will be playing the First Doctor in the 2017 Christmas Special.
  • Genesis of the Cybermen: The Mondasian Cybermen will return in the final two-parter, and the trailer implies they'll be in their original design. The origin of the Mondasian Cybermen is a story Peter Capaldi has already said he wants to see done, so it might make sense to do it in his last season finale. If that's the case, it will be interesting to see how Missy fits into that picture...and what of Moffat's Radio Times synopsis noting that a character the Doctor's "sworn to protect" dies in this story? (Nardole? Bill? Missy? Clara? Someone else?) And the regeneration issue?
    • Confirmed.

Series 10 and/or the 2017 Christmas special will finally make Twelve's Myth Arc clear... so what is it?
Both Ten and Eleven's individual seasons eventually turned out to be parts of a gigantic Myth Arc: Ten came to terms with the Last Great Time War and his status as the "last" Time Lord. Eleven dealt with the Order of the Silence, which turned out to be related to his saving Gallifrey. Twelve's arc initially appeared to be his quest to return to Gallifrey — but the Series 9 finale resolved that and made him a fugitive from the Time Lords again over Clara's fate, so it must be something bigger than that or his relationship with her. Moffat has commented that Twelve's story will really begin in Series 10, but now that it's been announced that the 2017 Christmas show is the end of that story, what is his Myth Arc going to be?
  • His relationship with Missy as they come to terms with each other. Given that almost half of the season, including the two-part finale, features her...
    • Confirmed as central to his Myth Arc. Although she only appears onscreen in about half the season's episodes (she notably sits out the midsection of the Monks 3-parter mid-season), she is an offscreen presence throughout due to the Vault Story Arc. He saved her from execution and has to watch over the place she was to be interred in, but is now just imprisoned in. In the Season Finale, he will risk everything to save her again. Twelve's Myth Arc is proving to the universe, if never himself, that he is truly a good man: At the end of it all when all hope seems lost, he will still do the right things — even at the cost of his life.
  • His realizing that Gallifrey was just where he was born and raised, so his dreams of reaching home the long way 'round actually relate to him embracing his true home — Earth.
  • Having decided that he became the Hybrid in "Hell Bent", realizing he must fulfill his destiny to be either the universe's destruction or its salvation when a new — or old — threat arises.
    • Jossed with Steven Moffat revealing that he and Clara are the Hybrid as Ashildr/Me theorized.
  • Finding a way to ensure the Time Wars can never begin again.
  • As suggested above, the Doctor revealing his past, answering the question "Doctor who?" at last.
  • Finding his way to the REAL Promised Land. Death and what may or may not lie beyond it has been a major theme of his tenure. He honestly doesn't believe a happy afterlife awaits him and that he's a lost soul. He helped Clara with the loss of Danny Pink. He had to accept the death of Clara even as he rendered her able to live beyond her natural life. He dealt with a false Heaven in "Dark Water", the second part of which was "Death in Heaven". He was trapped in a false Hell in "Heaven Sent", which was followed by "Hell Bent". And both of these stories were part of season finales. If Gallifrey was once the closest thing he had to a Promised Land, something he could work towards, as of "Hell Bent" it isn't anymore. And since then he's had to accept letting go of River Song so she can meet her fate in the library. If Series 10 is his final season, or even if it isn't, it will ultimately involve him discovering that there is a true Paradise beyond this universe, one where the empathy, compassion and even love that he's given so much of to others will finally be repaid — a reassurance that he is not a lost soul, but someone who will be rewarded for his Doctor-y deeds when all is said and done.
  • Finally confronting whoever/whatever it was that drove him to run away from Gallifrey in fear, as teased in "Heaven Sent".
  • Finally realizing how loved he is in a Grand Finale that brings back all of the key Moffat-era companions and recurring and/or beloved secondary characters either to help him or to be there as he regenerates, ala "Journey's End" or the denouement of "The End of Time". Yes, this means Amy and Rory Pond would return along with Clara Oswald and River Song — plus Idris, the Paternoster Gang, Kate Stewart, Osgood(s), Ohila, the General, Danny Pink, and Ashildr/Me just for starters.

There will be more stories set on other planets
This article points out that few Twelfth Doctor stories have taken him to other planets so far — though it's clear he's visited quite a few of them with Clara or on his own, those were mostly offscreen. Of the alien worlds central to his onscreen adventures in Series 8 and 9, Karn, Skaro, and Gallifrey were pre-established settings, and not much was learned/discussed about Karabraxos, Mendorax Dellora, and Darillium. The writer notes that if the Doctor's breaking in a new companion in Series 10, this would be the time to break out the really exotic locales of all of time and space.
  • Jossed. Only "The Pilot", "Smile", "Extremis", and "Empress of Mars" involve other planets, with all the other stories either confined to Earth or space stations, due to the Doctor having to keep to The Slow Path guarding the Vault. "The Pilot" and "Extremis"'s off-world scenes are brief and only flashbacks, respectively, with no exploration of societies, mores, etc. "Smile" involves a human colony.

There’ll be another "Peladon" story.
"The Curse of Peladon" –- from the Third Doctor era -– was an allegory for Britain & her relationship joining what was then called ‘Common Market’. It wouldn’t be too much of a reach for a story to mirror #Brexit.
  • Probably too late for one in Series 10, but something similar — not necessarily Peladon, but an analogy nonetheless — might fit into Series 11. Especially if Capaldi stays and Scotland doesn't...
    • Capaldi is not staying for Series 11, so this is looking a lot less likely.
  • Jossed, but with a twist. How about another Ice Warriors story instead — one that turns out to be a prequel to the Peladon stories, explaining why the Ice Warriors were involved?

The Flood will return as the villain in the premiere or the 2016 Christmas Special
In a clip from the filming, Stephanie Hyam's character appears to be possessed by water, which could mean that the Flood is returning.
  • However, "The Waters of Mars" was set a few decades in the future and Bill is from The Present Day. If the Flood was on Earth before "Waters of Mars" took place, why would it need to use the Mars crew to infect Earth?
  • Jossed twice over:
    • The Christmas special "The Return of Doctor Mysterio" went with a different returning villain, the Shoal of Winter Harmony/Harmony Shoal brains.
    • A watery lass says "Exterminate" in the final Series 10 trailer. Turned out that the Daleks were secondary antagonists in the season premiere instead, with the primary one being a new creature who was watery, not water. Given that this episode was intended to not only introduce Bill but allow new viewers to get into the show after a few years of near-Continuity Lockout, and is even titled "The Pilot", it makes sense for the most popular villains to be part of its action. With Missy central to both the mid-season 3-parter and two-part finale and the latter also serving as a Cybermen story, the Daleks' best bet for an appearance this year was in the season opener, and so it went.

The Fisher King's race will appear again
Considering the fact that while they may not be Time Lords, they do have technology that even they thought wasn't possible (manipulating souls). It would be interesting to see the two races come into conflict.
  • Jossed.

Miscellaneous episode plots and premises
With Series 10 featuring seven standalone episodes, a mid-season three-parter, and the traditional two-part finale, there should be time for Breather Episodes and non-Story Arc driven adventures again. What might they include?
  • The Twelfth Doctor finally encountering a Historical Domain Character, since he won't be doing so in the pre-season Christmas Episode.
    • Jossed.
  • Another UNIT-related episode, which may or may not involve the season's Big Bad. Bonus points if it turns out to be the Minister of War adventure, which is known to UNIT in the future. It helps that "The Return of Doctor Mysterio" has a Sequel Hook with one of the Harmony Shoal brains taking the body of a UNIT soldier.
    • Jossed: UNIT would have appeared in the Monks trilogy, but for actor unavailability.
  • At least one episode revolving around a recurring villain that isn't the Daleks, the Cybermen, and/or the Master/Missy: The Sontarans, the Zygons, the Autons, and/or the Weeping Angels are all possibilities.
    • In 2016, the Season Finale of the spinoff Class worked in the Weeping Angels...
    • "The Return of Doctor Mysterio" did this by elevating the previous Christmas Special's secondary villains the Shoal of the Winter Harmony to the principal villains. And it ended with a Sequel Hook ( one of them has taken over a UNIT soldier) too.
    • The Movellans of "Destiny of the Daleks" appear in the first trailer (see below for how that might play out).
    • The Ice Warriors have been confirmed as coming back! (It's Mark Gatiss's script for the season.)
    • The February 2017 teaser, which ends with a shot of both old and new villains, has a creature that may or may not be a Weeping Angel. Twelve never has had a chance to face off with the most famous new series villains (the "Hell Bent" cameo doesn't count)...
      • Jossed; they're not involved in any episodes of Series 10. They could be in the 2017 Christmas special, but more likely the show will bring back the Daleks for that one.
  • A classic series character/race who hasn't yet had a new series appearance finally gets one. It doesn't have to be a villain; how about Twelve meeting a classic companion or helping the Draconians again?
    • Confirmed with the Movellans, who get a cameo in "The Pilot". As a bonus variation, the Mondasian ("The Tenth Planet") Cybermen are returning in the Season Finale, with the original 1960s design to boot.
  • A "Doctor-lite" episode á la some of Ten's adventures ("Love & Monsters", "Blink", "Turn Left"). "Flatline" in Series 8 was a borderline example as Clara's A Day in the Limelight episode, but Twelve still had a lot of screentime and relevance to the plot. Series 9 had two companion-lite episodes ("The Woman Who Lived" and "Heaven Sent"). So how about a story focusing on Bill? Or one focusing on an original character, as "Love and Monsters" and "Blink" did? Or a beloved recurring character like the Osgood "sisters" or Kate Stewart? Or even a villain?
    • "The Lie of the Land" might be it. It has the Doctor in the grip of a mass delusion and Bill as the only one who isn't affected by it, thus putting Character Focus on the companion for an episode. For bonus points, as the conclusion of the Prophets of Truth three-parter she'd get to be a "true" heroine, and if she's to be one season and done it makes sense to give her time in the limelight.
      • Jossed for "The Lie of the Land", as the Doctor turns out not to be brainwashed, although Bill is the one who saves the day.
  • The Doctor finds a way to mend his fences with Ohila over the events of "Hell Bent", especially if Series 10 doesn't make Gallifrey a major part of its Story Arc. The announcement that this will be Twelve's last season makes it more likely that both she and Gallifrey will show up at some point, as do Missy and Saxon!Master's presence.
  • Most seasons of the revival have at least one episode that offers a twist on the usual formula — Bottle Episode, A Day in the Limelight, Slice of Life ("The Power of Three"), Found Footage ("Sleep No More"), etc. As-yet-unused (by either the classic or revival series) Episodes this show might use include:

The name of the Doctor will confirm that he's the Hybrid
We've never really found out why the Doctor keeps his name a secret... So maybe during Series 10 we find out the name of the Doctor will confirm that he is indeed the Hybrid of prophecy, and that's why he doesn't want people to know it. If he is indeed a half Time Lord, half human (as implied in "Hell Bent"), maybe his parents decided to give him a human name, so revealing that would confirm he's a hybrid. Maybe his name actually is Basil, as he told Osgood in "The Zygon Inversion"?

Davros will return
He has a bad case of the Joker Immunity virus and even though he was dying the last time we saw him, he hasn't actually died yet and who knows? Maybe Missy's "clever idea" has to do with bargaining for her life by saving Davros' and teaming up with him! I mean, can you just imagine the sheer amount of chaos and destruction Missy, Davros and an army of Daleks could cause together?!
  • Jossed, as the Daleks' only role this season is as a cameo in "The Pilot".

The Dalek episode is a spiritual sequel to "Destiny of the Daleks".
The first trailer for Series 10 features a clip of the Movellans, who appeared in "Destiny of the Daleks". Given that the Daleks have been confirmed to appear, then there's a chance the Dalek episode(s) might be a spiritual successor to this classic series serial.
  • Sort of borne out. They weren't the primary antagonists of "The Pilot", but yep, the Daleks were fighting Movellans again in their setpiece.

Missy wants to team up with Davros to conquer and/or destroy Gallifrey.
Given her history she'd have a major chip on her shoulder when it comes to her homeworld, which is now at its most vulnerable — hiding at the end of time, and as far as the audience knows without a leader now that Rassilon's exiled and the Doctor's forsaken his Lord President title. It's almost guaranteed she knows just where Gallifrey is, and Davros/the Daleks would jump at the opportunity to attack the remaining Time Lords. She'll try tempting the Doctor with trying to cripple Gallifrey in some form too.
  • With the reveal that this is the Twelfth Doctor's final season, this could well be the plot of either the Season Finale or the Christmas Episode that will be the Grand Finale for Twelve, as it would be a logical climax to his Myth Arc and also allow a chance for Clara, his only other companion, to be worked in as previous companions were in Ten and Eleven's finales.
    • Jossed. Confined to the Vault, she was on the sidelines of the mid-season three-parter with the Monks, while the Season Finale tangles her up with Cybermen and her previous self.

Nardole's time as ruler of Constantinople will become a Chekhov's Gun
Something he did, said, or witnessed during that time will become a plot point in a later episode, prompting The Doctor to go back there and see for himself what Nardole did.
  • Jossed.

The Doctor initially won't accept Bill as a companion
This analysis of the February 2017 teaser notes that Bill's voiceover suggests she has three pivotal encounters with the Doctor, during which she comes to understand his complexity and what it is to be him and to travel with him. Having had two bitter experiences with loss of late — losing Clara Oswald to the grave (even if she's Only Mostly Dead now, he still doesn't have her) and his key memories of her to a mind wipe, and then bidding his final goodbye to River Song — he may not want anyone to develop emotional closeness with him again, to carry the risk of losing another loved one. "The Return of Doctor Mysterio" established that he's taken Nardole on both to stave off loneliness and to make sure he has a Morality Chain (thus avoiding the mistakes he made when he didn't, or couldn't in the case of "Heaven Sent", create new bonds after loss), but the bond between them isn't a "classical" companion relationship. With Bill, he initially cannot bear to accept her as a companion and rejects her, but their paths keep crossing intentionally or not — perhaps the university becomes a "base" for the season, as Coal Hill did in Series 8 — and he comes to open his hearts again when he realizes how much he misses that "classical" bond.
  • Confirmed, but played out over a shorter time span. In the denouement of "The Pilot", he tries to mind wipe her, and it's suggested that he has made a promise to someone that forbids him from taking on new companions. But he decides not to mind wipe her after she reminds him (without her realizing it) of his and Clara's endgame, and then says "what the hell" and extends companionship to her as well, damn said promise and, perhaps, fear of loss.

Missy will regenerate, be trapped permanently, or die
Saxon!Master's last bow was in "The End of Time", Ten's final story, and Missy completely sat out Eleven's tenure. Given it's been rare for the Master to persist in the same form across incarnations of the Doctor — only Tremas!Master, who spanned Doctors Four through Seven, can make that claim — when Twelve goes, so goes Missy, possibly for good. This would further the concept of Series 11 being a clean slate for Thirteen, and if s/he appears again, it will be in a new form.
  • The March 13 trailer shows a wooden woman saying "Doctor" in what sounds like Missy's voice . . .
    • Well, the wooden woman has nothing to do with the Master, so that's jossed.
  • Also, Saxon!Master's coming back, which might be a sign of a big development for his later self . . .
  • Confirmed: Missy apparently dies during "The Doctor Falls", with no hope of regenerating due to taking a full blast from her predecessor's laser screwdriver, which injured her so thoroughly she could not muster the ability to do so.

The "Extremis" three-parter will involve the Minister of War
Episodes 6, 7, and 8, respectively titled "Extremis", "The Pyramid at the End of the World" and "The Lie of the Land", are confirmed to be a three-parter involving Missy and the corpse-like "Prophets of Truth". Photos also reveal they take place in what looks like The Present Day or close to it. Now, fans will remember that back in "Before the Flood", O'Donnell mentioned "The Minister of War" as a Noodle Incident that the Doctor has yet to experience. It has also been theorized that the Minister is a pre-existing character, such as the Master. Given this, and the fact that as a three-parter this story is likely to be large-scale and epic, perhaps this is what O'Donnell was talking about.
  • Now, if the Minister of War is the Master, maybe it's Saxon? Because it was just confirmed he's coming back, and he did serve as the Minister of Defence once . . .
  • Jossed: Missy is not an antagonist in this arc, and the Monks give Earth Laser-Guided Amnesia upon fleeing, so only the heroes remember they were ever there.

We'll finally see Missy's TARDIS
It's been hinted that she has one ever since "Death in Heaven", but it's never actually been seen. The middle episode of the three-parter, "The Pyramid at the End of the World", involves a visit to a far-future Earth where there's no more life, and this story has been confirmed to have two Masters. I think it's about time we got to see Missy's ride for a change.
  • Jossed for "The Pyramid at the End of the World". She's not even in that episode.
  • Looking Jossed in general since her presence in the finale involves her traveling with the Doctor as a companion.

"The Empress of Mars" takes place in the past.
Two things: One, it takes place on Mars, and there are Ice Warriors. In the present day of the Doctor Who universe, the Ice Warriors no longer live on Mars, although they do keep tabs on the Solar System. Two, Victorian soldiers are involved in the plot. As far as I know there's never been an episode taking place in space (which for the purposes of this WMG means "not on Earth") that's confirmed not to be taking place in the future, and it would be interesting to finally have an episode taking place in the past (or present) that isn't set on Earth.
  • "Genesis of the Daleks" took place in the past, for sure.
  • Confirmed by the trailer, which features Victorian soldiers. Furthermore, the Doctor Who Magazine synopsis reveals that the story takes place in the mid-1800s, with the Doctor, Bill and Nardole traveling back in time to investigate who managed to leave the message "God Save the Queen" on the surface of the Red Planet, revealed in a NASA photograph in The Present Day.

"The Eaters of Light" is a Breather Episode.
The season finale, "World Enough and Time"/"The Doctor Falls", is guaranteed to be epic, especially given the rather ominous title of the latter episode. "The Empress of Mars", coming right after the big, epic Prophets of Truth three-parter, also sounds fairly serious. Therefore, "The Eaters of Light" will be the last relatively lighthearted adventure of the Twelfth Doctor's run, because as the Christmas special is likely to be the regeneration episode, that will be serious as well.
  • Partially confirmed: It and "Empress of Mars" are both relatively more lighthearted than the Monks trilogy and the season finale.

The title of "The Doctor Falls" has a twist in it.
Sure sounds like the Doctor will be defeated in that one, possibly for good, right? But a lot of episode titles deliberately don't tell the whole story, and it could mean many different things:
  • The Doctor falls to an enemy — Missy, Harold Saxon, the Cybermen...
    • Partially Confirmed: The Cybermen inflict lethal injuries to the Doctor several times throughout the course of the story. Surprisingly, neither incarnations of the Master end up doing him in, even though they toy with the idea and attempt to leave him for dead, with the Saxon Master far more willing to do so than Missy.
  • The Doctor falls from grace in some way, ala "Hell Bent".
    • Jossed: The Doctor does not stray from his principles, though he struggles to avoid falling apart at the very end.
  • The Doctor falls physically. There's a black hole in this story — which might be just waiting to swallow a hero up.
  • The Doctor falls in love. With Missy, perhaps, in his desperation to redeem her?
  • The Doctor falls into depression over not being more of a hero.
  • It could be a callback to "The Day of the Doctor": The Doctor Falls...No More!
    • Partially Jossed: The Doctor incurs a temporary death, so in a sense, he does fall no more, but this line is never spoken in the episode itself.

When Missy and the Simm-Master meet...
Now that it's been leaked that Season 10 will include the first ever multi-Master episode, we can start guessing how two incarnations of the Doctor's old enemy will interact. Keep in mind that different Doctors always seem to bicker upon first meeting, so... any ideas?
  • Some truly epic Chewing the Scenery Ham-to-Ham Combat that puts all meetings between multiple Doctors to shame?
  • Flirtation? Yeah, I know they're the same person, but given how narcissistic he is it wouldn't be surprising.
    • Confirmed. When Missy pins the Master against a wall, he is shown to get a bit flustered. They certainly like to compliment each other (in flirtatious tones), as well.
  • Both of them will try to pull an Eviler than Thou, and either one will succeed or both will fail. Considering the Master's penchant for betrayal, this seems likely.
  • Missy could be the cause of Simm-Master's regeneration too if he tries to pull something over her.
    • Partially confirmed. Although the Simm-Master doesn't try to betray her, Missy does cause his regeneration. She stabs him in the back after choosing to stand with the Doctor rather than run away with Simm-Master.
  • They bicker and have a rivalry about who's the better Master, pointing out each other's flaws. However they come to like each other and form a Villainous Friendship, which meta-wise is meant to appease people who feel They Changed It, Now It Sucks! with the Master.

The multi-Master story will explain what happened to him after "The End of Time".
Either there will be time travel to the time Gallifrey was rescued (applying to the below theory), or after going with Rassilon he's been sealed up in what's likely a Fate Worse than Death. If it's the latter, their team-up will happen when Missy busts her younger self out of Time Lord jail, and it spirals out from there. Their team-up will end when either the Simm-Master regenerates into a young Missy (probably a little girl to save on getting a look-alike) or possible even a new incarnation entirely (no one said it was a direct transition).
  • Confirmed, but not in the above-listed details.

Someone will point out how ridiculous the Mondas Cybermen look
At which point, they will prove their merit as Cybermen by brutally killing that person.

It will be revealed whether or not Missy hears the sound of drums.
So far, there has been no reference to whether or not Missy hears the sound of drums implanted in the Master's head as a child. Since she's teaming up with Saxon, there will be a proper resolution as to whether or not she can hear the sound. And if she doesn't, it'll be revealed why not (besides Rassilon's plot in "The End of Time" being foiled, of course).
  • Played With: She shows a peculiar fascination with a four-tone alarm in the spaceship in "World Enough and Time".

Bill will be the one who kills the Harold Saxon Master, leading to his regeneration into Missy
This is why the Doctor befriended Bill. Missy told him when she was in the vault.
  • Possible, but not for this reason. Missy does not actually remember that as Saxon, he was responsible for Bill becoming a Mondasian Cyberman. Saxon seems to have set this up by way of ruining Missy's potential Heel–Face Turn, knowing that the Doctor will be heartbroken and enraged to realize what happened, thus encouraging her to think Then Let Me Be Evil. But Bill, now that she is a Cyberman, might indeed be the one to kill him.
  • Jossed: Saxon is killed by Missy.

    Other Characters 
Clara will make an unannounced one-off return a sequel to "Sleep No More". Can't have her wandering the universe when she's still infected, can we?
  • The Doctor presumably fixed her, as well as the other survivor, same as he erased the ghost-writing's effects at the end of "Before The Flood". Even if he didn't, the nature of Clara's current state means that the infection probably couldn't make any progress!
  • While Mark Gatiss did claim to be working on a "Sleep No More" sequel shortly after it aired, and reiterated this the following year, that episode was by far the worst-received of Series 9, in part because the sleep crust monsters were so ludicrous. Put simply, there's no viewer demand for a sequel, and bringing Clara into it would just add fuel to the fire! With the confirmation that Gatiss's script for Series 10 is an Ice Warrior story (his second after "Cold War" in Series 7), it looks unlikely to have connections with "Sleep No More".
  • If people don't want a sequel as such, there could just be an off-hand mention that the Doctor managed to stop the transmission somehow, to avoid What Happened to the Mouse?.
  • Given the confirmation that Gatiss' story for this season is about the Ice Warriors, this is looking Jossed.

If Clara's heart ever starts beating again, it will drive her insane the same way as the Master.
We know the Master was driven insane by being unable to ignore his own heartbeat(s). If Clara's heart starts again (for whatever reason), she might not recognize the sound and be unable to ignore it.
  • Seemingly jossed, as she only had a brief cameo in "Twice Upon a Time".

     2016 Christmas Special 
Potential plot elements of the 2016 Christmas Episode
  • Returning to Gallifrey to mend fences over the events of "Hell Bent" now that there's enough water under the bridge. This would placate fans who were frustrated that "Hell Bent" didn't focus strictly on what had become of Gallifrey, and would also fit in with the Doctor amending his creed with "And if you ever are [cruel or cowardly], always make amends", which would be properly heartwarming stuff for Christmastime. No one's ever said his world doesn't have a Christmas-style holiday. It might also allow the show to reintroduce characters such as Leela and/or Romana.
  • Setting up the Series 10 Story Arc as "The Snowmen" set up Series 7B's. Especially likely if they go with a Gallifrey-related story.
  • Reuniting with one or more family members.
  • Assisted by a minor character he helped in the past, by way of repaying their debt to him.
  • An encounter with The Krampus — it stands to reason that if Santa Claus has a place in the Whoniverse, so does his dark counterpart.
  • Facing off with the Weeping Angels — angels are key Christmas iconography (and "Voyage of the Damned" had the Heavenly Host); besides, isn't it about time Twelve battled the most popular new-series specific enemy? So far in his tenure they've only had cameos ("Hell Bent"); their last non-cameo was way back in Series 7A.
  • Undoing How the Character Stole Christmas. "Turn Left" was a variation on It's a Wonderful Plot, "A Christmas Carol" took care of Yet Another Christmas Carol, and "Last Christmas" has a touch of Gift of the Magi Plot with the Doctor and Clara's mutual lies coming to light, leaving a How the Grinch Stole Christmas! variation as the last Christmas-specific stock plot for the show to cover. Not to mention this could be a hilarious vehicle for Missy — maybe that "clever idea" she had on Skaro was a wonderful, terrible, awful idea!
    • Alternately, it could take inspiration from Christmas songs rather than Christmas literature or film. Imagine Capaldi, say, running into weaponized versions of twelve drummers, eleven pipers, etc, all so he can rescue a character named Miss Partridge who's trapped in a pear-shaped cell on a space station shaped like a tree?
    • "Silent Night" suggests a wide range of possibilities as well...
  • Encountering a being who wields snow and ice powers ala Jack Frost or the Snow Queen — such a character could be a hero, a villain, or something in between. Or would this be too similar to "The Snowmen"?
  • Standing in for Santa Claus in some way — which could be as ambitious as taking the real thing's role, or as simple and silly as going incognito as a Mall Santa.
  • In a Rhyming Episode or a Musical Episode, neither of which the show has done before. Then again, is the latter too hacky at this point?
  • Alternatively, Moffat is trolling — again — and this will be Bill's introductory story! Photos from the first days of Series 10 filming have revealed that her first episode involves snow, after all.
    • All of the above are Jossed. "The Return of Doctor Mysterio" is a take on superhero comics/movies featuring original characters interacting with Twelve and Nardole, the Bumbling Sidekick to River Song introduced in last year's Christmas show.

Steven Moffat has confirmed "a guest companion" will appear alongside Twelve in the 2016 Christmas show. Who will s/he be?
  • Original character possibilities:
    • Someone who might become a companion further down the line, as happened with Donna Noble ("The Runaway Bride") and Wilfred Mott ("Voyage of the Damned").
    • Someone who has a relation to the upcoming companion, Bill, in the way that "The Snowmen" featured one of Clara Oswald's echoes by way of setting up the Impossible Girl mystery.
    • Someone related to a previous companion.
    • Bill — if it turns out that Moffat was trolling about her not appearing until Series 10 formally begins.
      • Jossed.
    • A Historical Domain Character. Unlike Nine, Ten, and Eleven, the Twelfth Doctor hasn't interacted with one of these onscreen yetnote . Instead he's met Robin Hood and Santa Claus (fictional Public Domain Characters) and an Odin imposter. Perhaps a Christmas Episode will finally give him an encounter with a real-life figure of the past. Extra points if the character has a tie to the holiday of some kind. Since the series probably can't get away with the Doctor visiting the Nativity and they've already used Charles Dickens in "The Unquiet Dead", candidates could include:
      • Clement Clarke Moore, author of "A Visit from St. Nicholas" (aka "The Night Before Christmas")
      • O. Henry, author of "The Gift of the Magi"
      • Peter Illych Tchaikovsky, composer of The Nutcracker
      • Virginia O'Hanlon, author of the letter to the editor that inspired the editorial
      • Someone related to the song "White Christmas" — songwriter Irving Berlin, original singer Bing Crosby, etc.
      • Frank Capra, the director of It's a Wonderful Life
      • Effectively Jossed, as the premise of this episode involves a superhero — continuing the aforementioned theme of the Doctor interacting with thought-to-be-fictional beings.
  • Returning character possibilities:
    • Captain Jack Harkness. Even before the Moff's announcement of a guest companion, this possibility was specifically sparked by a Facebook post by John Barrowman himself. As the article points out, with Moffat effectively retiring from the Whoniverse after Series 10, he might want to give one of his other creations a Grand Finale along the lines of the one River Song received. The dramatic possibilities of the Captain encountering the Doctor after so many years — and tragedies — for both of them are legion; perhaps both characters will find some grace when their paths cross again? Not to mention that it could serve as a Fully Absorbed Finale for Torchwood — on the other hand, is wrapping up a Darker and Edgier show like that really the province of a family-friendly Christmas show?
      • Jossed. At Wizard World Comic Con Chicago in August 2016, Barrowman said Captain Jack would not be returning to the show before Steven Moffat's tenure as showrunner ends.
    • Shona, since she's not becoming the formal companion despite fan hopes that she would. A Christmas-specific companion might be a fun variant on a theme.
    • Osgood (at least one of her, anyway), with the Series 9 Zygon two-parter confirming she gets on well with Twelve.
    • Susan, to finally wrap up one of the show's oldest dangling plot threads.
    • A previous Doctor! The fanbase would rejoice over another multi-Doctor adventure, and Twelve hasn't had one yet save for his "Day of the Doctor" cameo.
    • An echo of Clara, with a Driving Question being whether he realizes who/what she is or not. Downside is that a lot of fans really want the show to move on from her at this point.
      • Unlikely; in July 2016 Jenna Coleman went on record as saying that while she might return to the show at some point, it wouldn't be for a while; this and the commission of a second season of Victoria also diminishes chances of Clara figuring into Series 10. (Although, with the subsequent announcement that 10 this will be Peter Capaldi's final season, she may be worked into the 2017 Christmas show at least.)
    • Idris, aka the manifestation of the TARDIS itself, from "The Doctor's Wife".
  • All Jossed. The guest companion is Nardole, the Bumbling Sidekick from "The Husbands of River Song", and the secondary companion (Bill being the primary one) of Series 10.

The 2016 Christmas special will feature the debut of the new companion
With the confirmation that the annual Christmas Episode will be the only new Who for 2016, it would make sense to use it as a lead-in to Series 10, which will debut in Spring 2017. What better way to do that than to introduce the new companion character? Previous Christmas specials have been used to introduce a Doctor ("The Christmas Invasion"), see Doctors out ("The End of Time", "The Time of the Doctor"), introduce a companion and/or a Story Arc ("The Runaway Bride" in hindsight, "The Snowmen"), or bring closure to secondary arcs ("Last Christmas", "The Husbands of River Song").
  • Jossed. imdb lists Episode 10.1 as her debut on the show, and the Christmas episode "The Return of Doctor Mysterio" is a superhero adventure with other characters — and the Series 10 secondary companion Nardole.

"The Return of Doctor Mysterio" will have a connection to "The Husbands of River Song".
  • In this preview clip, a Freeze-Frame Bonus shows that the building the Doctor is in is the "Harmony Shoal", eerily similar to the group who wanted to buy Hydroflax's head from River Song, who were called "the Shoal of the Winter Harmony". This could possibly establish "The Return of Doctor Mysterio" as a Prequel to "The Husbands of River Song".
  • Other evidence can be seen in the character of Scratch. He was a dealer who was on-board the spaceship stated above, who has the ability to conceal items in his head by removing half on his head, which a diagonal slit is cut across his head. Photos from "The Return of Doctor Mysterio" show a man who has the same diagonal slit like Scratch, and Aleksandar Jovanovic's character (the man who holds the Doctor, Nardole and Lucy Fletcher at gunpoint in the clip above) is seen to have the same diagonal slit on his face, albeit faintly.
  • As a bonus, the synopsis states this:
    This Christmas sees the Doctor join forces with a masked superhero for an epic New York adventure.
    With brain-swapping aliens poised to attack, the Doctor and Nardole link up with an investigative reporter and a mysterious figure known only as The Ghost. Can the Doctor save Manhattan? And what will be revealed when we see behind the mask?
    • The origins of King Hydroflax, anyone?
    • Confirmed! The villains are indeed the Shoal of the Winter Harmony, and their true nature is revealed — they're sentient brains who prefer humanoid host bodies.

"The Return of Doctor Mysterio" will have a Karkus quip.
How could they resist referencing the one other superhero-based character to appear in the series, waaaaaay back in "The Mind Robber"?
  • Jossed.

     2017 Christmas Special 
In the upcoming 2017 Christmas special, we'll see the First Doctor
There's been a lot of talk going around and articles released concerning this potentially happening, although the role he'd be playing in the story is up for speculation.
  • The most popular rumor seems to be that it would reveal both Doctors' sides of the events of "The Day of the Doctor".
  • Confirmed. One is indeed returning, played by David Bradley, who is now portraying the First Doctor for real instead of in a docu-drama. Whether it will involve the Time War remains to be seen.

"The Doctor Falls" will end in a cliffhanger leading straight into the Christmas special
The descriptions for the season finale sound incredibly ominous, and we know there's a regeneration coming up. Furthermore, the description of "The Doctor Falls" says it's "time for the Doctor's final battle". With all that, the Christmas special picking up right where the season finale leaves off seems likely.
  • Steven Moffat has gone on record as saying that the Christmas special will be an uplifting story as deliberate contrast to the Season Finale: "So, it will be a tale of redemption, and hope, and deciding to carry on, instead of being a tale of the Doctor falling." This suggests that it's possible for "The Doctor Falls" to have a cliffhanger ending, but not the usual ominous one. More likely, it will be along the lines of the Twelfth Doctor's previous post-season Christmas specials ("Last Christmas" and "The Husbands of River Song") in that it will be a coda to the season and era that shows how far he's come in a positive sense after he's faced his fears and demons in "The Doctor Falls".
  • Absolutely Confirmed: The big twist at the end is that the Doctor is actively resisting the need to regenerate, so the TARDIS ferries him to the one place he needs to go to convince him it's for the better- a run-in with the First Doctor, where he meets his original self, before he ever regenerated at all, so he can see what it was like back when he was defiant toward change.

It will involve the First Doctor, "The Tenth Planet" and a Stable Time Loop.
The reason why the Mondasian Cybermen appeared in the Season 10 finale will be revealed as the First Doctor during his first encounter be transported to the current era, aka the story where he would regenerate for the first time. He will arrive as part of The Stinger, confused since he was busy stopping Mondas from siphoning off Earth's energy. After meeting each other, the 12th Doctor will finally complete the Stable Time Loop of saving Gallifrey by telling the 1st Doctor about it, thus beginning the long process. Once the plot is done and the Doctors save Gallifrey, the 1st and 12th Doctor will return to their own era. In a bit of poetry, the 1st and 12th Doctor will be from points in time where they're about to regenerate.
  • Alternatively: Operation Exodus, mentioned in "World Enough and Time", is the plan to attack the Arctic Base during "The Tenth Planet", and during the Christmas special the Twelfth Doctor will have to venture down to Earth in 1986 and stop them. He'll encounter his first incarnation, who famously sat out the third episode because William Hartnell was too ill. Together, they'll have a hidden adventure the First Doctor won't remember, on account of their timelines being out of sync, and then they'll both head towards their regenerations.
    • Moreover, the First Doctor appears to be complaining about not wanting to regenerate, so he knows something is up with his body. This is very feasible and could even retroactively explain what pushed him over the edge as something beyond "wearing a bit thin".
    • Confirmed: This special is indeed set during "The Tenth Planet". It looks like we'll have some extra insight about what brought One's life to an end.

The special will feature the Valeyard.
The regeneration we see in "World Enough and Time" and "The Doctor Falls" leads to the creation of the Valeyard. It will be revealed that his plot during "The Trial of a Time Lord" is to try to prevent all the loss and pain Twelve experienced. Twelve will, in trying to stop him, give a Patrick Stewart Speech which the Valeyard won't listen to (so he'll still go back to put Six on trial). However, when Twelve does regenerate into Thirteen, his own speech will give him peace.
  • Alternatively, perhaps the Valeyard will turn out to be an equivalent to The Watcher. The Watcher helped prepare Four for his regeneration and serves to aid Time Lords who "aren't ready" (which Four handled well). The Watcher actually draws his personality from the current Doctor and they know that when they merge with him a bit of their current mindset will carry through. Four was optimistic about the future and so The Watcher was a helpful quiet figure who, when joining with the Doctor, lead him to become "The Nice One" (Five). Twelve is depressed and fears the worst part of himself, so this time The Watcher becomes an amalgamation of the darker sides of his nature. Seeing him, Twelve runs, not yet ready to regenerate but knowing he must do so without The Watcher (aka The Valeyard) or he will become evil when it does happen. However, he also knows that this watcher knows how to think like him, so he needs the First Doctor's help, someone to think in a way he's no longer able to help guide them to escape. In the end, they escape the Valeyard who, now that he can no longer merge with the Doctor, instead heads to Galifrey, intent on gaining the Doctor's regenerations etc.
    • Jossed. The first trailer and Children in Need clip didn't drop any hints remotely in that direction and looked far too busy with other things to have time for such a plot development. Word of God also reports that this, like Moffat's last few Christmas Specials, will be lighter and more humorous than the two episodes that preceded it. Come November's end it was revealed that the antagonists are all-new "glass people", the sort of one-off villains common to the Christmas specials.

At least part of the special will take place during World War I or II.
The recently leaked set photos have what seems to be the Twelfth Doctor and the First Doctor in a battlefield-like setting, with several people dressed in what appears to be solider uniforms.
  • This seems to work against the idea that the story will be an alternate perspective on "The Tenth Planet" — why would they leave that crisis to check out ordinary human war?
    • Confirmed: The battlefield is in the First World War, as confirmed by early official promotional materials. There's even a joke in the Children in Need clip in which the Captain is confused and disturbed by the Twelfth Doctor referring to it as World War I!

The 2017 Christmas special will be a variation on the "It's A Wonderful Life" or "This Is Your Life" trope
Twelve and One will revisit places and times where the Doctor has made a difference. Since One won't remember anyway, they could even revisit places other incarnations still in his future have saved worlds and lives. Or, keeping with the Christmas season, it could be a variation on A Christmas Carol with One as the ghost of Christmas past, and possibly Clara as present or future.
  • Possible. If Clara does appear, it's probably going to be a surprise cameo, and with the all-new threat of the Glass People as the central crisis it doesn't look like there will be much time to visit other settings and characters, though the Daleks have something to do with things, and the ravaged world they travel to could be a post-Moment or otherwise ruined Gallifrey, with the former an alternate timeline that exists until the Doctors all play their roles...
    • Jossed that the Doctors re-visit places where they'd made a difference, unless a single Dalek munitions-planet that some other regeneration blew up counts. In fact, the one historical event they visit (the 1914 Christmas Truce) is all the more meaningful because the Doctor didn't make it happen: ordinary humans did.

One will treat Twelve as a "companion"
It will be revealed that Twelve's real reason for not wanting to regenerate isn't because he doesn't want to change, but because he's just tired and can't appreciate the beauty in the universe anymore. He spends his life trying to save people and then, he loses some, saves a few and there are just more people to save. It all feels pointless. This time, instead of it being a "two doctors" story where he bickers with his earlier self, he's going to pretend not to be the Doctor. He's going to let his younger self take charge and solve whatever problem they have but in doing so he's going to get a chance to see the world through the eyes of a companion and understand why the world needs a Doctor, as well as being reminded through his younger self's words about all the good things there are in the universe that he stopped appreciating at some point.
  • Jossed. The Children in Need clip, which takes place relatively early in the story, has Twelve prove to the confused One (when they enter the former's TARDIS) that he is his future self via regeneration energy.

The title of the special will be "First Christmas" or "The Doctor Rises"
It would make sense on several levels for this to be the case. The special will feature the First Doctor, goes back to the beginning of things, seems to harken back to the first time the Doctor ever regenerated, it would serve as Book Ends to "Last Christmas" as well as Peter Capaldi's and Steven Moffat's tenures as a whole, and it will be the first story with Chris Chibnall involved, who will probably write for the first scene of the Thirteenth Doctor just as Moffat did when he took over from Russell T. Davies with Matt Smith. Alternatively, we could have an inversion of "The Doctor Falls", as in "The Doctor Rises", since the special is said to be uplifting and positive.
  • Very, very Jossed: The rumored title was "The Doctors", implying a lot more would be involved than we thought. The official title is "Twice Upon A Time", again Jossing the suggested ones.

The First Doctor will finally get to say "I simply will not give in!" before regenerating
Those were originally supposed to be his last words in the original script for "The Tenth Planet" but they didn't end up in the final episode. This would be a good opportunity for him to say them.
  • Semi-Jossed: One never says this phrase word-for-word, but he does express this intention.

Reece Shearsmith will cameo as the Second Doctor
Because it's Moffat's final episode, and he could pull one last fastball on us.
  • Jossed: We don't see any more of Two than the original regeneration-footage from "The Tenth Planet".

The First Doctor will be credited as "Doctor Who"
  • Jossed

"Twice Upon a Time" will be themed around the need for Twelve and One to embrace the possibilities of change.
When last seen, Twelve was refusing to regenerate, and when he overhears One's voice in the distance, One seems to be dismissing the thought of regenerating himself as "nonsense". Whatever heroic feats the pair of them may undertake in the Christmas special, the real accomplishment they'll achieve during their adventure(s) will be to realize that regeneration isn't just necessary for their survival, but it offers an opportunity to start life anew, with a fresh perspective and a more hopeful outlook. Hence, One will return to his own companions ready to be "renewed" as Two, and Twelve will set aside his world-weariness and cynicism enough for his subconscious to open up to any possible outcome for his next life ... even an outcome that he's never tried before, like being Jodie Whittaker.
  • Essentially confirmed.

The Doctor will receive a dose of zectronic energy
The Doctor was shot with zectronic energy in Steven Moffat's first broadcast Doctor Who story — the 1999 Comic Relief special "The Curse Of Fatal Death", which ended with the Doctor regenerating into a woman. Zectronic energy wasn't specifically stated to have brought about the change, but it would explain the ending of that story, and provide a rationale for how the Doctor can change sex this time around. Moffat's had this one up his sleeve for Bookends for a long time.
  • Jossed. The episode's theme about accepting death and cherishing memories is far too serious for that.

Mark Gatiss is confirmed as playing "a resonant echo in the whole Doctor Who story" according to Peter Capaldi. This could be...
  • The Valeyard — though the promise that this is a funny, uplifting regeneration story would work against a character this serious having a role. Or might he be Played for Laughs?
  • The Watcher
  • A genderbent echo of Clara Oswald (did all of her splinters have to be female?)
  • Yet another incarnation of Rassilon
  • Yet another incarnation of the Great Intelligence
  • Yet another incarnation of the Master — the first, perhaps?
  • A heretofore unseen relative of the Doctor — his father, perhaps?
  • A young First Doctor
    • All Jossed. The Radio Times synopsis confirms that Gatiss is playing a World War I soldier swept from battle into the Doctors' adventure. See below for what his significance might be.

Mark Gatiss is playing the Brigadier
He's called the Captain in the official release, so he could be a younger version of the Brig. The Time Stands Still scene appears to be in a trench battle during World War I. However, the trailer also implies some sort of Time Crash has happened.
  • Thank you, I thought I was the only one who caught that vibe.
  • Could also be an ancestor of his, as the Brigadier's family had a long military tradition. In which case, his surname of "Stewart" won't be revealed until his last scene, in which we'll also see him posting a letter home from the front to his fiance, a Miss Lethbridge.
    • This is far more likely as the Radio Times synopsis revealed this man is saved from seemingly inevitable death in World War One to be part of the adventure with the Doctors, which means he can't be the Brig himself.
  • Confirmed that the Captain is a relative of the Brigadier, either his grandfather or his great-uncle depending on whom you ask.

Mark Gatiss's Captain — a World War I solider — is a "resonant echo" because he's...your guesses here!
Besides the Brigadier or a relative thereof, there are other significant things he might be.
  • The latest theory to make the rounds of fandom is that he could be a young Gilbert MacKenzie Trench, the Real Life architect who designed the blue police box back in 1929. Stable Time Loop in the making?
  • A theory broached at Reddit is that he's Captain Noel Chavasse, a Real Life doctor in the Royal Army Medical Corps who would earn two Victoria Crosses for his life-saving bravery. He died in action in 1917. This would fit the idea of the two Doctors being inspired by humanity's example. However, he wouldn't inspire the Doctors to specifically accept a Loss of Identity and regeneration...
    • Except that his apparent first question of the two Doctors is whether either of them is a doctor. He probably wouldn't be asking for another doctor if he is one. At most, if he needed help in performing an operation or the like, he'd be just as open to the assistance of a trained nurse or med student, so would probably ask if they had "any medical experience" instead.
  • Captain Mel Pond, aka River Song. We never actually saw young Melody regenerate into Mels, so there is room to add another incarnation, ala the War Doctor. And we know this episode will feature at least one other gender-bender regeneration.
    • But how did she travel back in time?
  • The antagonist — his identity either isn't real, or it is but he's black-hearted (see below for other possible antagonists for this story).
    • Jossed.
  • An ancestor of a companion of the Doctor's, most likely Clara Oswald or Bill Potts.
    • All Jossed. He's a Lethbridge-Stewart.

Ben Jackson will make a cameo
If Polly is appearing, then it's likely Ben Jackson will, given that he was also present during the First Doctor's regeneration in "The Tenth Planet".

The Twelfth Doctor will notice there are "round things" in the First Doctor's TARDIS.
At which point, the First Doctor will get annoyed at him and chastise his future self for calling them that, correcting him by referring to them by their proper name, "roundels". Maybe he'll even wonder which one of his later lives forgot that/thought of that misnomer and Twelve will quietly bemoan the immaturity he had as Ten and Eleven.
  • Jossed. Twelve says nothing about One's TARDIS decor at all, although he does show his younger self up by piloting One's version without a hitch.

We will see the First Doctor use the Sonic Screwdriver for the first time in televised canon.
He has never done so before, the closest thing he has being the signet ring. Twelve will probably see him use the ring and make a comment similar to when he criticized the Sonic Trowel River had in her possession. Perhaps One will retrieve the original penlight screwdriver or Twelve will lend him his- and One is sure to make a remark about how it's supposed to be used on only screws and that it's ridiculous to think of using it any other way else until Twelve tells him he'll have a lot of time to fiddle around with it and make it do more. It might even result in a Stable Time Loop where the Twelfth Doctor gives his original self the idea to start carrying one subconsciously (because you know he will forget all this due to asynchronous timestreams and all that), and we know Two started carrying one as of "Fury of the Deep". And the chances of it appearing in his possession will become very high if this plot ties into the one from the 50th where the Doctors needed to calculate how to move Gallifrey like they did the door, as there is an enormous amount of time to work with between one and twelve to figure out the calculation over hundreds of years.
  • The sonic screwdriver's software was only used to calculate how to disintegrate the cell door in Day of the Doctor, not how to lock Gallifrey into a pocket universe. One of the Doctors specifically tells the War Council that they're using their TARDISes to do that, and several of the holograms in the General's war room show various Doctors working the TARDIS console's controls to advance their share of the calculations.
  • Jossed: One never uses Twelve's screwdriver, and calls it a "ridiculous buzzing toy".

The Thirteenth Doctor's debut will be loaded with sexual innuendo up the wazoo!
She will most definitely say something about her new Dalek bumps, maybe that she's developed a pair of faults.
  • Or maybe there's be something more subtle, e.g. it may take her a while to get her balance because her pelvis is wider than he'd been used to.
  • Jossed: She doesn't have time to do more than say "Aw, brilliant!" upon seeing her reflection before the TARDIS pitches over and she's flung out the doors, plummeting towards the Earth.

The Twelfth Doctor's Conclusion
In "The Time of the Doctor", many details connected to past episodes of the Eleventh Doctor's tenure, going all the way back to "The Eleventh Hour" but most notably "The God Complex". So, what are some plots that could connect to the Twelfth Doctor's tenure?
  • "Deep Breath": Did the Doctor push the Half-Face Man, or did he fall? Is he a good man?
    • Unlikely to be brought up, as the latter question was pretty definitively answered "Yes!" in "The Doctor Falls".
    • Jossed; the issue is not addressed.
  • "Mummy on the Orient Express": Who was GUS, and what was his motivation?
    • Jossed — the antagonists are all-new "glass people", unlikely to be associated with him.
  • "Under the Lake"/"Before the Flood": Who is the Minister of War that UNIT is aware of? (And with that in mind, if the Captain turns out to be the Brigadier's ancestor...)
    • Jossed; if the Minister is coming, it'll be later on.
  • "Face the Raven"/"Heaven Sent"/"Hell Bent": Don't the Time Lords and/or Ohila have some reconciling and apologizing to do with the Doctor, and vice versa? And Rigsy, Anah and Anahson never repaid him and Clara for helping them at such a horrible price.
    • Jossed; the only pre-Series 10 character to return is Rusty the Dalek.
  • "The Empress of Mars": Why was Missy concerned about the Doctor?
    • Unlikely if Missy isn't actually appearing. The Doctor was probably just distressed to see Missy being on good behavior anyway.
    • Jossed; Missy's story seems to be done with.
  • Bill's Return
    • Confirmed by the trailer!
  • Clara's Return: The first and last face the Twelfth Doctor will see
    • Confirmed that he sees her again; Jossed that hers is the last face he sees.
  • Nardole's Return: Maybe some origin story for Nardole — who is he?
    • Jossed: His character arc effectively ended in "The Doctor Falls", there were enough hints of a Dark and Troubled Past dropped in that and earlier episodes to suffice for his backstory, the Doctor knows what happened to him (unlike with Bill Potts, whom he believes to have died), and he probably would have been announced for this episode if he were turning up.
    • Confirmed that Matt Lucas reappears, but only to say goodbye and enjoy a last cuddle. (And to canonize that he has invisible hair.)
  • Stars: Twelve hoped there would be stars as he almost died in "The Doctor Falls". Perhaps stars will be the last thing he sees as he regenerates, with the help of the TARDIS and/or Bill when they realize what he wants.
    • Possible unless Heather's return in "The Doctor Falls" counted, owing to her star-shaped eye flaw. Explained here.
    • Jossed; Twelve regenerates in the TARDIS.

Other Doctors will appear (besides One, Twelve, and Thirteen)
The line from the trailer, "We're trapped inside a single moment" almost sounds more like Tom Baker than Peter Capaldi. Plus, both Radio Times and The Mirror have brought up rumors that the plot involves how all the Doctors were rounded up to save Gallifrey in "The Day of the Doctor", including how Twelve's famous Death Glare was actually during his regeneration. And with the Radio Times revealing that the Daleks have some part to play in this story, and the possibility that the ravaged wasteland the Doctors travel to is Gallifrey post-Moment...
  • Jossed that the actual Doctors or Gallifrey appear ... although various memories of intermediate Doctors are holographicly displayed by the Glass People, causing a bit of a Future Me Scares Me moment for One.

Just one additional Doctor will appear (besides One, Twelve, and Thirteen)...
... namely Two, in a re-creation of Patrick Troughton's original post-regeneration scene. And he'll be played by one of Patrick's sons, whichever one can be made up to look more like their dad.
  • Jossed: One's appearance uses Book Ends of footage from "The Tenth Planet", leaving no room for a fresh-filmed appearance by Two.

Susan will appear
As noted elsewhere on this page, one of the biggest plot threads dangling in the classic series: The Doctor promised to return to visit Susan, but he never did so on-screen as opposed to the Big Finish audios, in which he revisited her as Eight and even had her son Alex as a companion for a time, though it didn't end well. Ten may have visited her prior to regenerating based on what Eleven said in SJA's "Death of the Doctor" — but on the other hand, the revival has implied that Susan is dead (for example, the Doctor and the Master are consistently called the only two remaining Time Lords). So during the adventure, the subject of One and Twelve never revisiting Susan is brought up. Prior to the end, either Twelve or One (or both!) are convinced to go back to her and see her again one more time.
  • Alternatively, she wasn't a Time Lord so the Doctor didn't think to mention her. In any case, this would also finally pay off the significance of her photo being on Twelve's desk at the university, as Susan was never discussed or referenced otherwise in Series 10.
    • Big Finish, something which goes through the BBC to ensure elements are canon-compliant, has recently released a short where Susan is confirmed as being a Time Lord with her being called back with the rest to fight. However, this actually backs up the theory more as the fact she could have suffered a bad fate during it — or the Doctor may not even know what happened to her — could serve as even more of a motivator for her to be visited by the Doctors one last time.
  • Jossed that Susan appears.

Mark Gatiss is playing The Colonel
He'll end the Twelfth Doctor's era because it was getting too silly!
  • Jossed!

It will involve the 1914 Christmas Truce
All Doctor Who Christmas Episodes have taken place, at least in part, on Christmas Eve/Day, even if only briefly. A World War I battlefield is a crucial setting in this story, the two Doctors encounter a British captain...when put alongside Steven Moffat's claims that this story will be an uplifting redemption-based adventure, these details strongly suggest this event will be incorporated into the plot. Perhaps the frozen moment in time is, in fact, during the truce?
  • Looking unlikely: The Captain is "seemingly destined to die" before he becomes part of the Doctors' story, so it doesn't sound like he's breaking bread with the enemy when time freezes over. The truce might take place after time is restored to normal, but how would that be depicted if the Doctors have to get on with their regenerations in 1986 and can't attend? Remember, this is only a one-hour special. However, the special is promised to have some small connection to Christmas, so maybe it will be worked in?
  • Confirmed: Twelve fiddles with the timing of the Captain's return, allowing the Truce to save his life and that of his German counterpart. Witnessing the Truce and how Twelve saves two lives by intervening is also crucial in that it convinces One to regenerate, despite knowing his future as the "Doctor of War", and may have helped establish Two's greater desire to protect humanity rather than just observe it as One often did.

The antagonist is...your guesses here!
Very little has been revealed, as of the Children in Need preview clip released November 17, about who or what the antagonist of this story is. The Captain appears to be an ordinary person who turns out to have an extraordinary role in the Doctor's life, and the inspirational example of humanity is key to the Doctors coming to terms with their lives. The only other characters in the first trailer are pre-established companions and a German soldier played by one of the show's writers.

Something causes the Time Crash the Doctors must fix — or alternatively the Doctors accidentally cause it via their reluctance to regenerate, and something wants to make sure they don't fix it. Moffat has teased "new monsters" for the Doctors to face and also dropped a hint that this story will explore how evil is usually part and parcel with irrationality and goodness with logic, but that they can switch places — so No Antagonist will not apply. "New monsters" do not necessarily preclude old villains appearing.

The Children in Need clip of the Doctors and the Captain in Twelve's TARDIS reveals that they have just fled a time-travelling alien from the World War I battlefield back to 1986 Antarctica. If it isn't actually Bill Potts in an innocent misunderstanding given her new abilities (after all, the Twelfth Doctor thinks she's a Cyberman and/or dead) or another benign being, is it the Big Bad? And even if it isn't, there has to be a villain at some point — who or what?

  • Time Lord-energy boosted Daleks, possibly led by Davros?
  • Rassilon, seeking revenge upon the Doctor over "Hell Bent"'s events?
  • Other Gallifrey-based Time Lords, for similar reasons as Rassilon (the Doctor did abandon his post and almost undid the Web of Time)?
  • The next incarnation of the Master/Missy, who has reverted back to the character's evil ways?
  • Another renegade Time Lord such as the Meddling Monk, the War Chief, or the Rani? It's most likely to be the War Chief given the setting of the Time Crash and the fact that in the Expanded Universe book Twelve Doctors of Christmas Twelve already encountered the Meddling Monk in the 1970s, taking that character out of the equasion.
  • Clara Oswald gone bad (i.e. she never returned to Gallifrey/the trap street), whom the Doctor would have to redeem?
    • Jossed — she's not an alien.
  • The Silence, as speculated in this Radio Times article about this very question? Twelve never faced off with them.
  • The Weeping Angels, the most famous Who villains Twelve never faced off with onscreen? While they have never been depicted as having time travel abilities, the Radio Times speculation article linked to below notes they could have New Powers as the Plot Demands.
  • The First Doctor because saving Time will force the regeneration and he doesn't want that, especially after seeing what he becomes in Twelve? He will remain sympathetic, however, and be convinced to let go and accept change, which in turn helps Twelve do the same.
  • The Twelfth Doctor for the same reason? After all, unlike One (who has companions) he has nothing Worth Living For as he thinks Bill is dead. However, he already filled a sympathetic villain role in "Hell Bent", and another story based around his stubborn defiance of the laws of time and space would be a somewhat insulting finale for him, especially after "The Doctor Falls".
  • The Cybermen yet again, given that this story takes place during the events of "The Tenth Planet" and right after those of "The Doctor Falls"? The First Doctor's "Have you no emotions, sir?" line in the trailer comes from the former story, and then there's Steven Moffat's tease that this story deals with (among other things) how evil is not always irrational. Alternatively, a new variety of Cyberman will be introduced in this special, along the lines of the Cyberking in "The Next Doctor". This would count as "new monsters", right? However, having the Twelfth Doctor defeat the Cybermen two stories in a row won't add anything to his Myth Arc.
    • Probably jossed; as the Radio Times points out the Doctor doesn't usually refer to Cybermen as aliens. They are appearing as The Cameo simply because this story takes place during "The Tenth Planet" — but they won't be the Big Bad.
  • An all-new character collaborating with the Cybermen, believing that their example is one to be emulated? On the downside, this would risk coming off as recycling elements of a previous and relatively unpopular Christmas episode, "The Next Doctor". And this character could be...
  • The Captain? Although all promo materials suggest he's not the villain, just a WWI soldier, no other name guest stars have been announced for this special and it would be a huge plot twist to have him turn out to actually be someone else, or alternatively to just be a human with an evil, or just misguided, heart.
    • Jossed.
  • The Minister of War?
  • A member, or members, of an all-new species capable of time and space travel? Perhaps...
    • The REAL Hybrid? Surprise!
    • Confirmed, but it's not the Hybrid. The BBC blog summary has revealed that they are "Enchanted glass people, who steal victims from frozen time." No previously established Who race fits this description.

Bill Potts will choose to become a Cyberman again for the Doctor's sake
A key theme of this story is the need to accept change, unwanted though it may be, and move on. But the Twelfth Doctor being pressured to accept regeneration and all the changes that come with it, including a loss of self, seems unfair to him given that Bill Potts didn't accept her transformation into a Mondasian Cyberman and in the end was freed from that form to Ascend to a Higher Plane of Existence rather than coming to terms with her situation. What's good for the goose is good for the gander, so as a loving gesture to help Twelve accept his imminent change and see the good in it instead of denying it to the point of death, she will tell Heather to turn her back into a Mondasian Cyberman permanently — one who's an individual, and good. This will mean the story avoids a Broken Aesop and satisfies the fans who were unhappy with the Deus ex Machina of her restoration in "The Doctor Falls".
  • Jossed: The Bill encountered in the Christmas special is long past that, and the only Cybermen to appear are in Stock Footage clips from One's and intermediate Doctors' pasts.

The Captain will become the Thirteenth Doctor's companion
As this episode has been confirmed as Bill Potts's Grand Finale along with Twelve's, she'll have to leave before he regenerates. Twelve doesn't deserve Dying Alone so the noble Captain will stay and go on to travel with Thirteen, meaning the speculation over who her companion will be was a moot point all along. It would be a great surprise development and explain the "resonant echo" business — a character who helps One, Twelve, and Thirteen.
  • Jossed: Thirteen's three (!) companions' actors have been announced, and none of them is Gatiss.

Alternatively, another character introduced will turn out to be Thirteen's companion
As of October 2017, the cast list for this story looks mighty slim — two Doctors, three companions with only one set for a major role, the Captain, and the minor role of the German soldier. There have to be more than these, so besides the villains this special will introduce the character who will be with Twelve as he regenerates and thus become Thirteen's companion. How awesome would a surprise companion be?
  • Jossed: It's now been announced that Jodie will have three companions, and none of their actors are listed for the Christmas special on imdb. And the final shot of the TV trailer reveals the Twelfth Doctor will be Dying Alone in the TARDIS.

The cast and crew are lying — Missy or her next incarnation will appear, reformed
Michelle Gomez and company have said more than once that "The Doctor Falls" is Missy's final appearance, but the Master has Joker Immunity, so there's no way s/he died for good in "The Doctor Falls". Either Missy or the next Master will appear and they will be on the side of good from the beginning and help save the day. This gives Twelve the satisfaction of inducing a Heel–Face Turn and brings this aspect of his Myth Arc to a Happy Ending. It would also help encourage him to move on with his life, reminding him that change can be a very good thing indeed.
  • Jossed: Missy doesn't appear and is not mentioned.

Thirteen's first words after regenerating will be...
  • "Well, I suppose this settles the "good man" question..."
    • Jossed: It's "Aw. brilliant!"

All of the Twelfth Doctor's Season Finales were tales of death and loss that always left him alone in the universe. He never even got to save said universe during his tenure — unless one counts "Hell Bent", admittedly a stretch. For his Grand Finale he will finally have a day in the sun where the antagonist is fully redeemed, Everybody Lives, and Time is restored to great celebration, something akin to "The Doctor Dances" or "The Big Bang" — which were both penned by Steven Moffat, the former being part of his first script for the series. Having a glorious triumph and perhaps reunions with characters besides Bill will help the Twelfth Doctor (and, of course, his original self) to accept regeneration at last, and he will Go Out with a Smile instead of rage and sorrow.
  • He never explicitly saved the universe. We don't know how far the invasions from other universes that he headed off in "Flatline" and "The Eaters Of Light" would've spread if he and his companions hadn't intervened.
  • The late-November reveal that the antagonists are an all-new alien race of "enchanted glass people" means that they aren't a set of villains that have to stay evil, like the Daleks. Perhaps they have a sympathetic motivation — the way the Doctor did when he extracted Clara from the timeline in "Hell Bent" — and are redeemable. Alternatively, they're Always Chaotic Evil and no one will mind when they're destroyed, so it's close enough to Everybody Lives to be a happy outcome.
    • Confirmed, apart from one feisty naked Dalek that jumps on the Captain's face. The Glass People turn out not to be evil and the Christmas Truce allows Twelve to save the Captain and his German counterpart. Bill and Nardole are confirmed as loooong dead, but their memories still pop up to say goodbye.

It's All Just a Dream — a Dying Dream — of the Twelfth Doctor
The Twelfth Doctor may have been revived by Bill's tear, but he's not actually up and about and the TARDIS hasn't brought him to meet his previous self. Rather, the events of the final scenes of "The Doctor Falls" and from there this story are all a Dying Dream of his current self as he prepares to regenerate, as he convinces himself that he wants to change and live after all. It would fit in with previous stories featuring him dealing with mental constructs, dream worlds, and simulations. So the First Doctor is a reminder of how far he's come since the events of "The Tenth Planet". The Captain represents humanity and its resilience, which has long inspired his lives' actions. This would also explain why there's No Name Given — he doesn't have one! Bill represents all of his companions and how no matter what became of them in the end, they were ultimately changed for the better for knowing him (and explains why Heather apparently isn't with her). Time Stands Still as a metaphor for not regenerating, etc.
  • Jossed

The Glass People are not the main antagonists and there's a Big Bad — either the Daleks or the Time Lords
If the Glass People are the principal antagonists, then this would be the very first NewWho regeneration story that does not involve the Daleks, Time Lords, and/or the Last Great Time War in any way, shape, or form. Especially given that he hasn't dealt with the Daleks (aside from cameos) or Time Lords since Series 9, it seems odd that the Twelfth Doctor's Grand Finale wouldn't involve them and instead go with an all-new one-off race so powerful it needs One's help to defeat (or redeem). So perhaps at the 2/3 mark The Reveal that the Glass People are, willingly or unwillingly, in the pocket of the Daleks (with or without Davros) or the Time Lords will be made, and the Doctors will have to deal with them too. (Alternatively, they're trying to fight this enemy themselves and that's why they're kidnapping people; they end up allying with the Doctor.) Supporting this theory:
  • There's apparently only one Glass Person with a speaking role, the Glass Woman.
    • Jossed, there are other Glass People who speak.
  • The rumors saying this story will work in "The Day of the Doctor"'s events — how can it smoothly do so if the Glass People are a completely separate threat?
    • Jossed, those rumors were only rumors.
  • The Glass People's ability to freeze time and kidnap specific people sounds a lot like the Time Lords' extraction process, which was crucial to the Twelfth Doctor story "Hell Bent".
    • Confirmed that it's a very similar process, but Jossed that the Time Lords play a part in it.
  • The Doctors' big confrontation with the Glass People takes place on a planet with a red sky...
    • Jossed: That's Villengard after the Daleks' munitions facilities were trashed by War, and the Doctor's "big confrontation" took place on their space/time vessel before he went there.
  • Radio Times has revealed the Daleks DO have a role in this story, but that doesn't necessarily mean they're a Big Bad; it could just have to do with the backstory — especially since the RT was allowed to reveal this in the first place.
    • Jossed that the Glass People are not the main antagonists; they just aren't evil antagonists. Daleks do appear, but the only one in a position of power is Rusty the renegade, who actually helps Twelve so that the Doctor can continue to hurt the other Daleks Rusty hates.

The Glass People, or at least the Glass Woman, are giants
The official "iconic" promotional image unveiled at the end of November has the two Doctors and Bill looking up at something apparently fearsome. Is it the Glass People, or just the Woman, who could be their leader and thus huge?
  • Jossed

The Doctors won't need to fight the antagonists to solve the crisis
"The Doctor Falls" was explicitly described by Steven Moffat as the story of the Twelfth Doctor's Final Battle, and indeed he fought the Cybermen to the death on his end. He can't have two final battles, so this adventure will not involve fighting and destruction, but finding another, peaceful way to stop the Glass People's kidnappings, ala some of Moffat's Christmas specials for the Eleventh Doctor ("A Christmas Carol" and "The Doctor, the Widow and the Wardrobe"). This would also gibe with the official synopses of the special describing its story as "magical" and "inspiring".
  • Unlikely given that the TV trailer teases a firey showdown in an industrial wasteland. But things initially looked like they would end in blood and tears in stories like "The Empty Child" and "The Zygon Inversion" too...
  • Confirmed: Twelve has to go somewhere rather dangerous to find out about the Glass People, but what he learns is that they aren't the bad guys. Indeed, it's a rare case where there are no bad guys, aside from a few creepy naked Daleks crawling around in the ruins of Villengard.

The Glass People are kidnapping the Doctor's previous human companions and acquaintances
For whatever reason — loneliness? A desire to warp his lives and stop his noble needs by stripping him of human influence? — the Glass People are deliberately seeking the Doctor's human associates through time and kidnapping them. They have targeted the Captain by mistake, believing him to be the Brigadier. This will not only explain Bill's presence (she's one of their victims, and this also explains why Heather isn't set to appear) but lead to a Continuity Cavalcade of previous regular and recurring characters via cameos as the Doctors rescue them, a sunshiny counterpart to the villain cameos in Eleven's Grand Finale "The Time of the Doctor". And their holding out hope for escape and/or rescue by the Doctor will show him "the resilience of humanity" and give him the hope both of his lives need to keep going, as mentioned in the official synopses.
  • Confirmed, but very different than the above: Turns out that Testimony abducts absolutely everybody at their moment of imminent death, but only to record their memories for posterity in a reverent, benign variant of Missy's "Nethersphere" scheme.

Mysteries surrounding Bill's presence
Bill managed to Ascend to a Higher Plane of Existence in the previous episode, heading out to travel the universe with Heather and believing the Doctor to have been Killed Off for Real. But is THAT Bill the Bill the Doctor encounters? For one thing, there's some fandom uncertainty as to what exactly she became — does she have a separate body already, or is she fully merged with Heather and would have to have one "made"? Other questions: Why has Heather not been announced as appearing in this episode? Why is the outfit Bill wears in the official promotional images NOT the outfit she's seen wearing in "World Enough and Time"/"The Doctor Falls" or in the actual "Twice Upon a Time" footage/photo stills? She wore the image outfit earlier in Series 10, but what's with the new badges on the jacket (a lightning bolt and what looks like a stylized American flag) and the sparkly shoes? Do the latter have to do with the Glass People, the principal one of whom is a woman? Meanwhile, Pearl Mackie has said that Bill's final fate will be "poignant" even as this is intended as a joyful, funny episode, and that there's a twist to her presence — likely ruling out death, but not something bittersweet. So...why is Bill in this episode? What crosses her and the Doctor's paths again? It could be one of many possibilities...
  • She's NOT the real Bill but an impostor — i.e., the Glass Woman in disguise, luring the Doctors into a trap by taking the form of someone Twelve cares about. Of course, the real deal could turn up later; perhaps she was taken prisoner so she could be impersonated. Or is all this too similar to the Zygon two-parter from Series 9, in which Bonnie impersonated Clara?
  • It's not the ascended Bill the Doctor encounters, but Bill from an earlier time period — after she became the Doctor's companion, but before the events of "World Enough and Time". This would explain her outfit, but not the new badges or shoes, in the iconic. On the other hand, she and the Doctor would have some very confused conversations in light of what the Doctor knows.
  • Bill's physical appearance can be explained by her new powers — she can simply choose her look as she goes like Heather does. Bonus points if this leads to The Reveal that she's Really 700 Years Old now.
  • Bill has simply been captured by the powerful Glass People and her new abilities aren't helping her, or being apart from Heather means she's Brought Down to Normal.
  • Bill is trying to help the Glass People but can't do it on her own. It might be because...
  • The Glass People are the original race whose spaceship leaked the fuel that merged with Heather — after all, it never was explained where the spaceship came from or who it belonged to — so now she and Bill are hybrids with a relation to them. This would relate to Heather's ability to use reflective surfaces to track Bill.
  • Bill realizes the Doctor is alive but in trouble and tracks him down.
    • Confirmed that the Bill in this episode is one of the Glass People, but she's also constructed from Bill's recorded memories and as much the "real" Bill as River's Library-recorded incarnation was the "real" River Song. The Bill who departed with Heather remains unaccounted for, although this Bill's remarks strongly imply that watery-Bill (wherever she may be) still has faith that the Doctor isn't truly dead.

Bill will basically steal screentime from the First Doctor, making the episode a case of Never Trust a Trailer
It could possibly happen, just like "Hell Bent" focusing more on Clara rather than Gallifrey.
  • Looking less likely from the TV trailer, which has a little bit of Bill but more of One. Also, don't forget that the Captain, a mightily important all-new Walking Spoiler character, also has to have a good deal of screen time to establish his significance — and Mark Gatiss gets billing before Pearl Mackie in promotional materials.
  • Jossed: One has a reasonable share of screen time, including some interactions with Bill as well as the usual bickering with his later self. If anything, it's the Captain who's left on the sidelines looking bewildered a lot.

The firey world where the Doctors confront the Glass People is...
  • Villengard, home of the weapons factories mentioned in "The Empty Child". The recent Radio Times reveal that Villengard is brought up in this story may well explain the firey planet and industrial complex seen in the trailers, where the Doctors have a showdown with the antagonists. "The Empty Child" suggested that the Doctor himself was responsible for the destruction of the weapons factories on that planet. Either this adventure will reveal that One and Twelve together destroyed them — and the Ninth Doctor talking around admitting this to Captain Jack is because, as it happened in a multi-Doctor encounter, he doesn't remember it clearly — or it's set after they were destroyed and the Glass People are trying to rebuild them, or use them for scrap in their scheme.
    • Confirmed: It's Villengard post-destruction, although the Glass People aren't the ones Twelve brings the group there to meet.
  • Gallifrey in an alternate/altered timeline. The red skies, broken pillars and shredded greenery suggest that not only haven't the two Doctors yet regenerated, they haven't played their part in the ending of "The Day of the Doctor", and as a result end up seeing what would have become of Gallifrey if the Moment were used after all and the planet destroyed. Since there is life there (spaceships zipping around, an exploding moon), the Glass People have perhaps settled there to take over the universe using whatever's left of Time Lord tech, such as the extraction chambers. The Doctors are then "summoned" by their other selves, and realize that the only way to stop the villains is to play their roles in saving Gallifrey instead of destroying it. This fits in with comments that the story has an It's a Wonderful Life feel to it.
    • Jossed. Gallifrey is only mentioned in a conversation between One and Bill, about what One might've hoped to find when he'd left in the first place.
  • Earth in an altered/alternate timeline. As pointed out by the website Blogtor Who, the Glass People are kidnapping Earth humans out of time, which could severely alter the course of the planet's history. The heroes could even still be at the South Pole as time is being altered! Supporting this idea is that "the resilience of humanity" is key to the story and the Doctor "finding hope in his darkest frozen moment" from it, according to the press releases. If this stretch of the story is set on another world, especially Gallifrey, what would humanity's example have to do with things?
    • Also Jossed. The Glass People return the people they take to their point of origin with no memory of what happened, so pose no threat to Earth history except when something goes wrong. The hope that inspires both Doctors is their witnessing the 1914 Christmas Truce.

The final shot of the TV trailer is NOT footage of Twelve's regeneration, but...
Would the powers-that-be really spoil half the final sequence of this special in a trailer? Especially after Series 10 pulled the rug out from under the viewer twice regarding his actual regeneration? What's actually being shown is one of the following precursors to the regeneration:
  • A trick, as in "The Lie of the Land"
  • Another abortive regeneration, as in "The Doctor Falls"
  • The Doctor weaponizing regeneration energy, as in "The Time of the Doctor"
  • A Dream Sequence, hallucination, or otherwise
    • Jossed.

Slade's "Merry Xmas Everybody" will be heard yet again.
Because it's pretty much Doctor Who's honorary Christmas theme song.
  • Jossed, sadly. The only parts of the story taking place on Christmas are in 1914, decades before the song was written.

Craig Ferguson will appear in an episode
Or a couple. Because, come on! Craig is also a Doctor Who fan, and one who was a fan alongside Capaldi! They've been friends since their youth and they were together in the punk rock band from which Capaldi's Doctor has been drawing the whole aging rock star vibe. It's just too good to let it pass. Besides, Matt Smith kept promising Ferguson that he would get him a guest role on Doctor Who, it's about time it happened.Jossed. He never did.

Guest writer speculation
Moffat has teased two big-name guest writers this season. As of June 2016, so far the announced writers have been him, Frank Cottrell-Boyce (a name guest, but "In the Forest of the Night" is no fan-favorite), Sarah Dollard and Mike Bartlett (experienced, with the former penning "Face the Raven" and the latter the creator of popular BBC drama Doctor Foster, but not "name"). That leaves a handful of episodes yet "unclaimed". Possibilities for the special writers might include:
  • Neil Gaiman: He wrote the wildly popular "The Doctor's Wife" and less-so "Nightmare in Silver" for Eleven, and has expressed interest in writing a Twelfth Doctor story.
  • Russell T. Davies: The first revival showrunner returns!
    • Jossed for both; Moffat confirmed that the two writers in question have never written for Doctor Who before.
  • Stephen Fry: He did write an episode back in 2006 for Series 2 (it would have been set in The Roaring '20s), but it went unmade when it was pushed back to Series 3 and he didn't have time to rewrite it to have Martha as the companion instead of Rose.
  • Peter Jackson: Well, Moffat's efforts to woo him into directing a Who story are well-known...
  • Edgar Wright: It helps that he worked with Moffat on the screenplay of The Adventures of Tintin (2011).
  • J. K. Rowling: She was offered the chance to write an episode in the early years of the revival, but was too busy wrapping up the Harry Potter series at the time. On the other hand, she's busy this year adding on to that franchise (the Cursed Child stage play and Fantastic Beasts and Where to Find Them movie).
  • It's possible that Rona Munro (see below) could be one of them. However, as mentioned below, she wrote for the classic series. Unless the Moff was referring specifically to having never written for the new series. With him, you never know.
  • It's confirmed that they're Rona Munro and Mike Bartlett, as the only writers for Series 10 who have never written for the new series beforenote .

The classic series writer returning for Series 10 will be . . .
  • Ben Aaronovitch: As a producer, Moffat is far too pragmatic to give a writing slot to someone just on the basis that they wrote for the old show, which was over twenty-five years ago when the landscape for sci-fi drama was wildly different. But Aaronovitch, who's currently riding a wave of popularity due to his Rivers of London urban fastasy series, is a known quantity who's proven he has mass (genre) appeal in the modern age. Hence, he's the most logical choice to bring back, well and above someone like Terrence Dicks (see below), who is mostly just known for writing Doctor Who. It also helps that one of Aaronovitch's two Who scripts was the beloved "Remembrance of the Daleks", one of the best-regarded serials of The '80s.
  • Bob Baker: Although not as well-known as Aaronovitch, Baker did co-write the Wallace and Gromit films, which easily translate to a more comedic and slapstick-heavy Doctor Who episode.
  • Terrance Dicks: He wrote or co-wrote serials for the Second through Fifth Doctors, and was script editor for Three's entire tenure. Given that Twelve is a throwback to early Doctors in many aspects of his personality and wardrobe...
    • All Jossed! It's Rona Munro, who wrote what turned out to be the Series Finale of the classic series, "Survival". She's penning episode ten (the last one before the two-part Season Finale), "The Eaters of Light".

Post-Release WMGs

    Series 10 Story Arc 
The Vault is the key to saving Gallifrey.
As seen in "Day of the Doctor", saving Gallifrey took the effort of all 12 Doctors that existed at the time of the episode, including the yet to be seen 12th Doctor. Given the massive Stable Time Loop of the event, it seems unlikely they'd show the final step off-screen. Behind the Vault is the technology and computational power that gives the final step to saving Gallifrey. It's also where the Moment, which was last seen under the War Doctor's possession and is the only thing besides Dalek Caan (which ended badly) who can break into the Time Lock and affect the Last Great Time War. Because the timelines hadn't synced up yet, the Doctor consciously put it there so nobody would have access to it, but subconsciously put it there so the massive Stable Time Loop would work. When 11 got a new regeneration cycle and thus knew he could have future incarnations, he partially remembered that there were 13 Doctors who saved Gallifrey.

By the time he started looking after the Vault, the 12th Doctor knows everything about its true purpose, and simply has to finish the last of its calculations so he can visit the last day of the Last Great Time War and save Gallifrey. Naturally, he's extremely protective of it as it's the crux of a massive Stable Time Loop. If anything within it would be screwed around with, it means Gallifrey would burn or worse and the 12th Doctor couldn't even exist at best. And at worst... yeah. Nobody else can get in or even know just what's in there until it's served its purpose, and even then no one should get in there since no one should have the power to break into the Time War. He's probably going to destroy the Vault once the loop is completed.

  • Jossed — It's just housing Missy, and its origins reflect the fact that an executed Time Lord needs to be carefully confined lest they somehow return to life. She isn't actually dead, though.

An incarnation of the Master is locked in the Vault
In "Thin Ice" we learn that whatever is inside the Vault is alive, and it scares Nardole by knocking four times . . .
  • Supporting this is that, between "The End of Time" and "The Day of the Doctor", it's still not clear how the Master survived to become Missy. Perhaps s/he is part of the Stable Time Loop of Gallifrey's rescue — or just a Stable Time Loop of his/her own — that the Doctor still needs to work out. (That said, s/he isn't the only candidate for knocking four times, as "The End of Time" and "Hell Bent" made clear.)
  • In "Knock Knock" the Doctor offers to tell the occupant the story of how people got eaten by the house, and then we hear the occupant playing "Pop Goes the Weasel" on a piano.
  • In the first trailer, one of the shots is her lying on what appears to be a piano. This links back to "Knock Knock", where the person in the vault somehow has access to a piano inside.
  • Steven Moffat's already confirmed that the "Vault" mystery will be revealed in "Extremis", so why would this mystery be used for only half a season on an unexpected identity? Therefore, it has to be someone recent that the Doctor has encountered: Missy.
  • If this is actually a past version of the Master as the present-time version of the Doctor's captive, it might provide a new explanation for why in Series 8 Missy says the Doctor "abandoned" her and left her for dead - possibly this will be the outcome of the Vault storyline, with the on-screen regeneration of the Simm Master to the Gomez Mistress as a result of the Doctor's negligence (or a cold-blooded choice to save someone else). The Doctor, having finally returned to Gallifrey in "Hell Bent", somehow ended up as the warden of the Master, who had himself returned to Gallifrey in "The End of Time". He made a vow to never shirk his duties and risk the Master escaping imprisonment to wreak more havoc, but with loneliness leading to him taking Bill on as his companion against his better judgement, the Doctor is getting distracted from his watch and the Master will eventually die, regenerate into Missy, and blame him for it — upset because the Doctor stopped paying as much time with her after 50 years and making her obsessed with regaining him as a friend; while nobody's happy locked up, the Doctor was dedicated himself to watching over the Master and "Knock Knock" would imply he often visits and talks with the Master, which in a twisted way could revive their friendship enough that losing his attention upsets the Master and regaining his friendship permanently becomes the Master's main goal, which when he regenerates, carries over to the mindset we see with Missy in Series 8 and 9.
    • There are some issues with this: 1) There are potential Reality Breaking Paradoxes involved; the Doctor saving Gallifrey pivoted on Missy uniting the Doctor with Clara Oswald, because it was Clara who convinced him he could do it. 2) The Doctor left Gallifrey pretty quickly in "Hell Bent" and there's no indication as yet that he ever returned. 3) Why would the Doctor agree to guard the Master at the Time Lords' behest? He owes them nothing at this point. 4) If the Doctor knows the Master's future as Missy, why would he worry about interfering with his/her life at all?
    • Alternatively, the Doctor is protecting the Master/Missy from harm, perhaps to ensure that their regeneration, etc. goes off as planned to prevent the aforementioned Reality-Breaking Paradox. Break His Heart to Save Him?
  • In the closing scene of "Oxygen" Nardole says that the Vault prisoner can sense the Doctor being infirm or dead, an urgent problem as the Doctor is now blind. Between this and the next episode being the start of the multi-Master arc, it would be more surprising for it NOT to be Saxon or Missy, as the only other characters who might be capable of sensing the Doctor's distress is the Doctor himself or someone very close and similar to him (i.e. a family member).
  • The opening scene of "Extremis" will show how the Doctor imprisoned Missy, who had taken control of a society.
  • Confirmed — it's Missy, and she was imprisoned in the Vault because she was somehow captured and scheduled to be executed on a planet that has this as their business. According to that planet's rules, her execution had to be performed by another Time Lord, so they called in the Doctor. He couldn't do it, however, but he did promise to guard the Vault her body was supposed to be placed in for a thousand years, which is why he's in his current situation.

If the Master is in there, they will be let out by...
  • ...their future or past self.
  • ...the Doctor, perhaps because he needs his/her help to solve a problem. (And as of "Oxygen" he's blind, so...) Or, given that the Doctor helping to free others from obligations, imprisonment, etc. is a major theme of this season, because the reason they are both effectively prisoners and the oath he took aren't actually all that noble.
    • With the Doctor in need of help defending Earth from the Prophets of Truth at the end of "Extremis", this is looking very likely.
  • Jossed. In "Empress of Mars", the Doctor lets her out but confines her in the TARDIS, in an attempt to give her a chance at redemption. This leads into the events of "World Enough and Time".

Inanimate-seeming objects turning out to be alive or swarms of living things will be a regular feature of this series.
As of "Knock Knock", we've had a puddle, a space-colony's architecture, the riverbed of the Thames, and a creepy old house all turn out to be made of, infested by, and/or constraining something unseen and dangerous. This pattern may well continue.
  • "Oxygen" has the smartsuits that turn out to be programmed to deliberately kill their wearers when the latter prove inefficient, resulting in a horde of them pursuing the survivors.
  • And in "Extremis", a virtual simulation of the Doctor turns out to be "alive" enough, despite not being "real", to send the actual living Doctor a warning about an imminent threat.
  • In "Empress Of Mars", what appears to be a golden statue lying prone as decoration on the Ice Warrior Empress's tomb actually is the Empress, in hibernation. When she's revived, the "gold" vanishes and she stands up.

Other candidates for the Vault
"Knock Knock" reveals that the Doctor does not like having to keep watch over his "prisoner", but made an oath to someone to do so. The prisoner has a morbid sense of humor, a connection to Gallifrey, and the Doctor feels a kinship with them. According to Nardole Earth would be threatened if it escaped, but there is the possibility that the Doctor is trying to protect it from the outside world, rather than the other way around. While the Master/Missy is the most obvious candidate, and the possibility that it's the Moment is discussed above, prerelease hype gladly spilled the beans on the Master/Missy's involvement. And it's hard to believe he'd still harbour affection for the Master/Missy after realizing that she paired him with Clara to create the Hybrid, leading to one of the most painful relationships of his lives.

With the reveal at the end of "Oxygen" that this prisoner can actually sense the Doctor being injured or dead, it probably will turn out to be the Master/Missy. But it could also be...

  • The Doctor's mother. Mothers have figured into four of the first five episodes, bar "Thin Ice", and the Doctor is silent when the Landlord asks him if he would do anything to protect his mother. It would also resolve an issue going back to "The End of Time" as to The Woman's identity, and possibly the Doctor's parentage. As a Gallifreyan at least, if not Time Lord, it might be able to sense the Doctor's distress/death.
  • The Valeyard — "The current Doctor's sick or dying? It's showtime!"
  • Susan Foreman, finally referenced in the revival at the top of Series 10, and add to that the Doctor being called "granddad" by Bill in "Knock Knock" ... Did something happen to Susan in the Time War requiring her to be isolated? Again, as a Gallifreyan she might be able to sense the Doctor's distress.
  • The Twelfth Doctor's Watcher — "The current Doctor's sick or dying? Time to prepare for the moment..."
  • An unknown relative of the Doctor — Again, Gallifreyan and family ties.
  • The REAL Hybrid — Surprise!
  • Clara Oswald
  • Ashildr/Me
  • One of the Doctor's past or future incarnations — "The current Doctor's sick or dying? What does that mean for me?"
  • In "Knock Knock", the Doctor is having a conversation with the prisoner of the Vault, and we hear piano playing coming from inside. The prisoner clearly hears what the Doctor is saying, but we never hear him answer back, only the music changes. Based on all this, the logical conclusion is that the prisoner is a sentient piano. Probably an evil sentient piano to boot.
    • Weakened somewhat by the fact that Nardole is surprised to hear the music and expresses indignation at the idea of the Doctor putting one in there, which implies there was not a piano in the Vault in the first place.
  • A Mondasian Cyberman. Who loves music. They have to be contained or they will delete all composers whose music they see as inefficient.
  • 'Amy or Rory. In "The Pilot", Bill says that it's rumoured that the Doctor has been at the university for 80 years. So he's been guarding the vault since the late 1930s. In "The Angels Take Manhattan", Amy and Rory were sent back to 1938. So what if something bad happens to one of them, something that corrupts him or her? And for reasons yet to be explained, s/he needs to be kept inside the vault? This would also explain why the Doctor said he'd made a promise to guard the vault. If it's, say, Amy, he certainly would've made such a promise to Rory. And using Amy in this story would allow Moffat to end his Doctor Who with the first companion he wrote, just like Davies did with Rose.
  • All Jossed: Again, it's Missy.

The Doctor will risk everything to save Missy in "World Enough and Time"/"The Doctor Falls"
The Moff's Radio Times synopsis of the former mentions that the Doctor will witness the death of someone he is "pledged to protect" and will try to undo it, and that friendship will motivate his actions. Given that Missy is featured in this two-parter and "World Enough and Time"'s title comes from Andrew Marvell's poem "To His Coy Mistress", this strongly suggests a Save the Villain adventure. It would be the ultimate potential Heroic Sacrifice for a Doctor to save a non-innocent, and would fit in with this series' theme of the importance of individual lives — that he would nobly risk his own for hers, not just out of friendship, but because it's the right thing to do.
  • If we look a little further in that poem, we get what could be seen as a reference to regeneration: "And while thy willing soul transpires / At every pore with instant fires..."
  • Given that the whole Story Arc of the Vault began because he chose to Save the Villain and pledged to watch over the Vault for 1,000 years, this is looking VERY likely.

The return of Susan is being set up
She might not come back this season, but it seems possible that Series 10 may be setting up a return at some point in the near future. There have been numerous references to classic Who as well as her so far this season, such as:
  • Her photo appearing in the first episode
  • The Doctor again being called grandfather
  • The Landlord saying to the Doctor how hard it is leaving a charge alone in the big wide world

There's also how the Doctor previously believed he was the last Time Lord, that his family was all dead, after he'd allegedly destroyed Gallifrey. Him believing her dead suggests that one way or another she ended up on Gallifrey during the war — and now Gallifrey's back. And she probably heard about the crisis of "Hell Bent" and what happened to him...

  • Jossed.

Regarding the Doctor's blindness
In "Oxygen", the Doctor gets blinded after having to lend Bill his helmet for a spacewalk. He seems to get it fixed with the medical equipment onboard the TARDIS — but at the end of the episode, he reveals to Nardole that it didn't work, and he's still blind. Nardole had just chewed the Doctor out for putting himself in danger when he has to guard the Vault, and one of the things he says is that if the Doctor were to return from a trip injured, the prisoner in the Vault would know about it.
  • Alternatively, it will be a reason for the Doctor to release the prisoner in the Vault: because he needs their help to fix his blindness, or to solve another problem. The ending of "Extremis" suggests he will release Missy to help him fight the Prophets of Truth — although she doesn't show up in "The Pyramid at the End of the World", the next episode, but rather the episode after that, "The Lie of the Land".
  • Jossed: It gets fixed by the Monks when Bill makes a Deal with the Devil to save the Doctor's life. Missy had nothing to do with it.

Someone will lay down their life to save the Doctor in "The Doctor Falls"
A major theme of Series 10 is how much the Twelfth Doctor cares about others — be it groups of people/beings, or just one person — and how much he's willing to risk to save them; his Chronic Hero Syndrome puts himself, his companions, and even Earth at risk, and is compared and contrasted with how antagonists in his episodes act to save who/what they care about. He ends up blinded in order to save Bill in "Oxygen", as well, but he saw it as worth the trouble. He could not execute Missy but will still hold to his oath to look after the Vault she's now imprisoned in for 1,000 years. But who has risked everything for the Twelfth Doctor? Isn't he important too?
  • Already, "The Lie of the Land" and "The Eaters of Light" had other characters stepping up to take his place in a Heroic Sacrifice. Notably, none of them actually died doing so. This does not rule out it being important to "The Doctor Falls", however.
  • Jossed: Actually, the reverse happens.

The Doctor will use the sonic sunglasses to compensate
He's wearing them in the last scene of "Oxygen", shortly before he reveals he's still blind. He's also wearing them throughout the "Extremis" trailer, to the point that Bill asks him why he's wearing them indoors at one point. Since he's hiding this, the sunglasses might come in very handy in that respect.
  • Confirmed — they let him see an outline of his surroundings, and can give him details on the species, gender and age of people in his field of view, but they don't give him more specific details about people or indicate light levels.

The Doctor was slightly brain-damaged on the spacewalk
Brains are oxygen-hogs, taking up 20% of the oxygen you breathe. As such, they are vulnerable to damage when someone is suffocating. Now, Time Lords are more durable than humans, and can survive thanks to their respiratory bypass system, but judging by what happened in "Oxygen", the logic still stands. Meaning the medical tech on-board the TARDIS did fix his eyes, so they're working properly — the problem is in his brain. There are plenty of blind people in real life whose handicap is due solely to brain damage, while their eyes are still perfectly functional. This also explains why it still isn't fixed — if there's one thing the Doctor definitely wouldn't want, it would be other people or foreign objects messing with his brain. And since Time Lord brains are far more complex than human brains, it's possible that no one but the other Time Lords — whom the Doctor is on bad terms with — would be able to fix the problem.
  • This is a sensible explanation. But then there really isn't anything stopping the Doctor from going back to Gallifrey to ask his fellow Time Lords for help — surely they have the compassion to attend to a war hero, torture victim, and now disabled man, who gave up good health to save an innocent life? They do owe him one after he saved their planet, and failed to pay up in "Hell Bent".
    • The Doctor has a history of being loath to have anything to do with the rest of his people. And given how he burned his bridges with the few high-ranking Time Lords he actually seemed to like in "Hell Bent", the chances of him voluntarily going to the Time Lords for help with his current problem is unlikely. Another factor is that the Time Lords, in general, have a history of being disdainful of other species, not to mention their Alien Non-Interference Clause, so why would they care about the actions behind how he was injured? Finally, the Time Lords messed with the Doctor's head way back in the classic series, erasing his memories of how time travel worked as a punishment. Odds are he wouldn't trust them not to mess with his memories or some such if he went to them for help with a brain injury.

"The Lie of the Land" will resolve the Doctor's blindness
In the final episode of the "Return of Missy and Saxon"/Prophets of Truth three-parter Bill is faced with having to kill the Doctor when he and the rest of humanity are afflicted by a mass delusion, leaving them in the thrall of the villains, according to the Moff's synopsis for the Radio Times. Finding there's no hope of making him see reason, and knowing it's not his fault, to save her own skin and the world she'll — with tears in her eyes — pull the trigger. It might be to kill, it might be just to wound, but it will trigger a regeneration. The Doctor will somehow manage to stop it, but it will not only heal his wound and break the delusion, but also restore his lost eyesight! Alternatively, Missy — who has been confirmed as appearing in this episode — will help their dear friend the Doctor by giving him some of their regeneration energy so he can heal. Of course, this also makes "The Lie of the Land" the story that will explain the regeneration energy seen in the Series 10 trailers. The only downside to this is that the Doctor and Bill will have to have a long heart-to-hearts talk afterward to alleviate her guilt. (Alternatively, someone else will harm the Doctor — perhaps when he can't go through with harming Bill — he'll do it voluntarily, etc.)
  • Jossed. Bill accepts the Monks' offer at the end of "The Pyramid at the End of the World" so that they'll cure the Doctor's blindness so he can escape imminent death. She shoots him in "The Lie of the Land" because she believes he's Brainwashed and Crazy, but it's actually a Secret Test of Character and a faked regeneration.

The Doctor has not told Nardole the truth about the prisoner in the Vault
Nardole is convinced that whatever is in the vault is a menace to Earth, and puzzled that the Doctor treats it so kindly. But setting the imprisoned/enslaved free of their jailers is a major theme of this season. Moreover, every episode/multi-parter has "villains" who aren't actually villains but turn out to be in thrall to either programming and/or beings with genuinely selfish/evil intent: Heather, the Vardi and the Emojibots, the sea creature, the Dryads, the smartsuits, and even humanity and the Doctor (in the forthcoming "The Lie of the Land", in which they're all Brainwashed and Crazy). And the Doctor tells his prisoner (when Nardole isn't around) that he's a prisoner too, bound to his still-unrevealed promise. This suggests that the Vault's resident is — if not innocent — at least not wholly to blame for their situation, and the Doctor, or someone else, will ultimately free both of them from their imprisonments, damn the consequences.
  • Jossed. "Extremis" reveals that Nardole knows it's Missy. He actually encouraged the Doctor to Save the Villain when he was about to execute her. But the Doctor must hold to the oath he took to watch over the Vault her body — living or dead — was to be sealed in for 1,000 years, and Nardole also knows that Missy is dangerous and could escape and wreak havoc if the Doctor isn't prepared to stop her. Even if she doesn't escape, eventually the oath will end and the Vault will open of its own accord, and the Doctor must be ready to confront her then.

Bill is not who she thinks she is, but rather is....
There must be a reason the Doctor not only takes so strongly to a young woman with no money, virtually no family, and no prospects in life that he decides to tutor her, but also decides that it is better to let her have her memories and from there make her a companion than mind wipe her so he can focus on the Vault and Missy. There must be a reason he risked his life (and lost his sight) to save hers in "Oxygen" when protecting himself for the sake of the Vault and humanity would render her death an acceptable loss. Beyond mere compassion, there must be a reason he is so concerned for her. And that reason is that she is actually far more important to the universe, or at least the Doctor, than she believes herself to be. Besides the possibility that she is the great-grandmother of Orson Pink, she could be...
  • Susan Foreman's daughter/the Doctor's great-granddaughter (discussed in detail in the folder for "The Pilot" below)
  • Another family member of the Doctor
  • An echo of Clara Oswald whose appearance happens to be very different
  • The daughter or granddaughter of Clara Oswald (somehow...)
  • Another incarnation of a different Time Lord, such as the Master, wiped of her true identity via chameleon arch
  • Alternatively, the descendant of another Time Lord
    • The War Council Time Lord the actress of her mum played is actually the same person as the mum. It would still explain quite a lot about her as said in the Pilot folder, her simply having that heritage, without her mother necessarily having been someone well established. If the mum was on a final regeneration or fob-watched herself, that would also explain how she could have died as stated.
  • The subject of a cosmic prophecy
  • The prisoner in the Vault
    • Jossed.

Alternatively, Bill will become...
In contemporary Who, companions start out as ordinary but become extraordinary as the season progresses. Rose became the Bad Wolf, Captain Jack became immortal, Martha walked the Earth, Donna became the Doctor Donna, Amy and Rory became the Doctor's family, and Clara became the Impossible Girl and half of the Hybrid. Following on from this, Bill will become...
  • A Time Lady
  • An adopted granddaughter of the Doctor (But only if she stays for Series 11)
  • The liberator of humanity and the Doctor in "The Lie of the Land".
    • Confirmed — she uses her mental image of her mother to break the Monks' hold on Earth. The Doctor didn't need liberating, though — he was only pretending to be brainwashed. In "World Enough and Time", she also becomes a Mondasian Cyberman.

The Doctor was guarding the Vault during "The Return of Doctor Mysterio"
"Extremis" reveals in a series of flashback scenes that the Doctor came to be the custodian of the Vault, making an oath to guard it for a thousand years, not long after he left Darillium. Nardole also catches up with him in these scenes, revealing that he's with the Doctor because River Song asked him to look after him. Given this, and that the Doctor has been based on Earth guarding the Vault for at least fifty years that we know of, this is probably what he was doing during the events of "The Return of Doctor Mysterio". If you think about it, in the episode the Doctor doesn't actually need to have done any time travelling at all, and Nardole has shown he doesn't object to the Doctor stopping hostile aliens threatening Earth so long as he doesn't have to travel in time to do it.
  • In addition, the Doctor first meeting Grant Gordon and keeping tabs on his adolescence probably happened between "Hell Bent" and "The Husbands of River Song", when he was travelling alone.

The Prophets of Truth / Monks are the Veritas from The Sarah Jane Adventures.
In the audio story "Judgement Day", they are aliens who kill everyone that lie because their own species was driven to near-extinction because of a lie, and they target Sarah Jane Smith for keeping the presence of aliens a secret on Earth. Eventually, they let her go because they realize that keeping that secret is actually better than not.

Aside from the name of the forbidden literature in "Extremis" being called Veritas, the Prophets of Truth themselves look very similar to the Veritas. Maybe they've come back to finish what they've started, only instead of killing everyone they will force humanity to believe one specific thing (why Bill will be immune is unknown), and not lie for their own good. They want to save the Earth from experiencing what their own world did, even if it means conquering and brainwashing everyone into submission.

Missy is not the real Master.
She's a what-if incarnation similar to the Valeyard, with only one life. The Simm-Master either never regenerated or did regenerate but kept the same form while fixing the deficiencies he had in "The End of Time". Missy might have been "born" from a repressed desire of the Master that he'd had for a long time... the want and need to be the Doctor's friend once again, which in her twisted way has been the drive behind all her actions. Neither Missy or the Doctor know this, however, and both think that she's the original Master.
  • Alternatively she is the Master, however spending time with the Saxon Master will have the consequence of them splitting into two entities via time paradox. Which isn't too different from how the Valeyard was originally intended to be the Doctor's real future self.
  • Or she is a Valeyard-like split, but with the capacity to do good unlike the original Master (the inverse of the Valeyard to the Doctor). Her slow Heel–Face Turn is genuine and she'll die to save the Doctor, most likely at the original Master's hands.
    • Jossed. She is the Master, but Saxon is determined to see she never makes a Heel–Face Turn.

The return of Saxon!Master happens when...
If it's in the Prophets of Truth 3-parter... (All Jossed)
  • The Prophets of Truth, who specialize in mass delusions, convince her that someone else is him or just make him appear to her — and others, including the Doctor — as an illusion.
  • Saxon, at some point in his timeline, decides to throw in his lot with the Prophets of Truth, or at least convince Missy not to help the Doctor as she might otherwise do under the circumstances.
If it's in the Season Finale 2-parter...
  • The story takes place in his/her past. Given that the other antagonists of this storyline are the Cybermen, including the Mondasian ones...
Possible for either story...
  • Missy's not-execution scrambles her Time Lord abilities, causing her past and present selves to be internally warring with each other (imagine arguing with him in a mirror, which would make for the promised face-to-face scene) and sometimes causing her to revert back to the form of Saxon.
  • He is the incarnation of the Master in the Vault, not Missy. The Vault could just as easily hold one Master as another. Perhaps they managed to switch at some point, or the Doctor put another one inside because Missy was "safer" free than Saxon would be.
  • Missy is actually a, if not the, pre-Professor Yana/Chameleon Arch Master. When she told the Doctor he abandoned her, she meant at a point before "The End of Time", perhaps in the early days of the Last Great Time War, and at that point he probably didn't recognize her. The later Saxon!Master returns to free his earlier self and set the stage for his existence.
    • All Jossed. She's a later incarnation, and Saxon is trying to stop her from making a Heel–Face Turn by turning Bill into a Cyberman, figuring that the Doctor will resent her when he learns the news. With the Twelfth Doctor indeed heartbroken, Missy appears to have decided Then Let Me Be Evil as of "World Enough and Time"'s Cliffhanger.

Saxon won't appear until the season finale
First off, the available information about "The Pyramid at the End of the World" and "The Lie of the Land" doesn't really suggest that Saxon will play any part in those episodes. The clincher, though, is Moffat's obvious displeasure with the decision to A) put a shot of Saxon at the end of the trailer that aired after "The Pilot", as particularly evidenced by the fact that he asked the audience at an early public screening of the episode to close their eyes before they could see the clip; and B) the formal announcement of John Simm's return a couple days after this, as shown by the clearly irritated tone of the statement he released in response to it. Now, the Moff doesn't have the greatest track record when it comes to hiding major spoilers about upcoming episodes — just look at the Series 9 finale, in which promotional material spilled the beans about Clara's death, the Doctor finding Gallifrey, and Clara's return — but in this particular case, the way he seems to have wanted Simm's return to be a complete surprise to the audience suggests to me that Saxon is involved in the story about Missy and the Mondasian Cybermen, and indeed that the early announcement of their involvement in the Series 10 finale may in fact be misdirection intended to conceal the Masters' true role in the story. I suppose we must wait and see.
  • Confirmed, as neither Master appears in "The Pyramid at the End of the World" and only Michelle Gomez has been listed as a guest star for "The Lie of the Land". He finally appears in "World Enough and Time".

Bill is immune to the delusion in "The Lie of the Land" because...
Nothing so far in Series 10 suggests Bill has anything that would render her immune to the Monks'/Prophets of Truth's brainwashing, which is powerful enough to affect the Doctor along with the rest of humanity. So she is immune because...
  • The Doctor performs some kind of Heroic Sacrifice to keep her free of the Prophets' control when he and humanity must give it up to the Monks to save Earth. (Yes, I know, again.) It's possible he gives up his free will to protect Bill in the hope that she will be able to defeat the Prophets in a way their simulations couldn't predict, even if it means he's risking his own skin as an unknowing slave. He might also give her information as to how to let Missy out of the Vault for help, now that the Godzilla Threshold has come, which would explain her presence in the episode. Perhaps because the Vault protects her, Missy is unaffected by the Monks' work.
    • But the Doctor is much more clever and powerful than Bill, who isn't even a particularly courageous companion when the chips are down (see "Oxygen"). Why does he think she can defeat them when they'll have him in their power to oppose her? Come to think of it, why doesn't he just admit he's beaten this time, go back to the TARDIS, and move on with his lives (as Clara convinced him to do in "In the Forest of the Night" when it looked like there was no hope for Earth then)? They don't need him to be happy, they just need the humans, and he can always find other races to protect. Or if that's too cruel and cowardly, why not escape and come back with an armada to fight the Monks and liberate the humans?
  • Her "communing" with Pilot!Heather affected her brain in some way back in "The Pilot".
  • She's not immune — everyone else is! The Prophets trick Bill into thinking everyone else has been brainwashed in hopes of her destroying the Doctor, who's trying to help her in reality, because she's the closest person to him. "The Lie of the Land" will be told from her viewpoint, setting up another tricky reveal at the end.
  • They're allowing her to not be mind-controlled and her being seemingly "immune" is not an accident or unplanned.
  • Something to do with her mother. Semi-Wild Mass Guessing here but she has been repeatedly mentioned.
  • She may have been in the TARDIS or similarly away when the brainwashing occurred, rendering her unaffected.
    • Why would she leave/abandon her friends during a crisis that threatens all of mankind (in "The Pyramid at the End of the World")? If she chooses to leave the Doctor's side or meekly submits to being sent back to the TARDIS, she's not much of a companion at all.
      • Could mean the Doctor tricks her into leaving, as he's done with other companions such as Rose, rather than her willingly going.
      • Alternatively, the Doctor could try such a trick, but Bill sees through it like she saw through the mindwipe attempt, and then it's likely back to the Heroic Sacrifice.
  • All Jossed: Bill's immunity seems to be connected to the fact that she is the one who ultimately agreed to make the deal with the Monks, in exchange for saving the Doctor's life (yes, it was a Sadistic Choice). The "being in the TARDIS when the brainwashing occurred" explanation may, however, apply to Nardole, who was sick with a nasty plague, and her mum did have a part in helping Bill prolong her immunity.

Missy will escape at the end of "The Lie of the Land"
The Next Time trailer for the episode reveals that Bill and Nardole let Missy out of the Vault in order to help them save Earth and the Doctor from the Monks. She will do so, but instead of letting herself be locked up again, she'll escape somehow, to eventually return in the season finale.
  • Jossed. She stays put in the Vault, and though she does leave it in "Empress of Mars" to help Nardole with the TARDIS, she's willing to go back at the end. In the end, the finale's jumping off point is the Doctor letting her take his place for a day in hopes she can learn to be good!

We will see the Master regenerate into Missy
Just to prove the point home that Missy is the Master and not some imposter. To avoid needing body doubles he becomes a little girl, allowing a long life to set up everything Missy did.
  • Partially Confirmed: We are told the Saxon Master will turn into Missy, but the actual moment this happens is not shown on screen. Whether this is a stylistic choice or a way of opening the door for something else to happen before the regeneration sets in is a mystery.

Missy is going to try get the Doctor to do a Face–Heel Turn
It was her intention when this incarnation first ran into the Doctor in a twisted attempt to salvage their friendship and would serve as Book Ends. Exactly why depends on whether or not she's faking her attempt at her ow Heel–Face Turn, with possible examples being:
  • If currently genuine, something happens that convinces Missy there's no point in her trying to "turn good". Perhaps she loses faith she can and/or starts believing the opposite happening to the Doctor is more doable.
  • If currently faking, she could be doing so in order to start getting closer and friendlier to the Doctor again, a closeness/trust she may use to try influence him with her philosophy. She did try get him to turn Bill into a vegetable and when he refused tried make him doubt his philosophy.
  • An attempt is unplanned as of "The Lie of the Land" but will be tried last minute, perhaps?
  • Jossed.

Bill will be the one to die in "World Enough and Time" — and actually stay dead and not be brought back in the next episode.
For several reasons, she seems like the most likely candidate:
  • The Doctor has already risked himself to save and protect Bill, most notably in "Oxygen".
  • She seems to be realistic in how she reacts to some situation in a largely relatably human manner.
  • To make it clear that travelling with the Doctor is not safe, and that Anyone Can Die is in full effect, especially since Steven Moffat has been criticized for chickening out of truly killing off his characters (River being uploaded to The Library, Amy and Rory living out good lives in the past, Clara being immortal and travelling the universe with her own TARDIS until she chooses to die). People are expecting something more to come from Bill's arc, specifically concerning her mother, but what if it gets brutally and quickly cut short?
  • Nardole dying wouldn't have as much impact, and Missy dying wouldn't matter since The Master always comes back.
  • It's been rumored for months that Bill will only be in this season.
  • Also, the doomed character is "someone [the Doctor] has pledged to protect". While he pledged to protect Missy in "Extremis", the trailers for "World Enough and Time" have Bill asking him to promise her she won't die as part of his plan to redeem Missy, and from there the BBC America/Syfy Latin America trailers reveal she faces conversion into a Mondasian Cyberman — effectively a living death that it might take a real one to free her from, unless the Doctor can figure out how to reverse the process. (More on this below under "World Enough and Time".)
    • A strong argument against this is that it would be hugely controversial. Bill is the show's first openly gay long-term companion and only second full-time companion who is a POC. Especially with Martha having already been viewed to have been treated poorly and overshadowed by Rose, Bill suffering from a permanent case of Bury Your Gays and Black Dude Dies First — especially in a grisly way, verging on Stuffed into the Fridge — is something that the BBC probably does not want to risk. In addition, Bill dying as a Cyberman would be a copy of the fate of Danny Pink in the Series 8 finale (and he was also black, for even more unfortunate implications).
    • Since the season began airing Pearl Mackie has gone on record as saying she doesn't know if she'll be in the Christmas Episode and/or Series 11, suggesting Bill survives this finale at least.
  • Jossed. While she is shot through the chest, she is ultimately Cyber-converted into a Mondasian Cyberman, so she's still alive. The question is whether the Doctor can reverse this or find another way for her to live in "The Doctor Falls".

Samantha Spiro is playing a Time Lord
We know she's playing somebody and word around is that it's a returning character. Her playing a Time Lord could explain how she's a new actress (to the show) apparently playing an old character.
  • Jossed. Going by her character name (Hazran) and the Radio Times episode guide synopsis of "The Doctor Falls", she is playing one of the few Mondasians who have not yet been converted into Cybermen, whom the Doctor must protect. It's possible that she'll turn out to be an established character in disguise, but there looks to be enough going on in this episode as it is.
    • She played one of the farmers.

The Monks' similarity to the Silence isn't coincidental.
Both of them are creepy aliens who manipulate memory for the sake of a conspiracy. We know from "Time of the Doctor" that the Silence are genetically engineered creatures, but from who or what? Maybe the Monks. Thanks to time travel the Silent Priests were made after the Monks' invasion, so maybe the Papal Mainframe used the latter as the genetic template for the former. The Monks' true form would probably resemble a Silent.

    "The Pilot" 
Heather wasn't an ordinary human to begin with
Take a look at her eye. That's an awfully specific "birth defect", and coupled with some other cues from her scenes before she's taken by the oil leads to the suspicion that she might have had some connection to aliens that she was unaware of from the beginning.
  • The fact that she surely wasn't the only one to look in the oil (we saw at least the Doctor and Bill look in too) and yet was the one to get specifically targeted by it, does lend some weight to that theory.
  • Well, it apparently targeted her because she wanted to leave. But yeah, that could be it. She might return by the end of the series.
    • With the suggestion that the oil was from a Cyberman vessel, she might appear in the Season Finale in which their appearance is confirmed (see below) — especially now that it's clear that Bill undergoes Cyber-conversion in it. Heather's time-and-space traveling, shapeshifting and communing abilities could be used to free Bill's soul, if nothing else, from her Cyber-ized body, allowing her to Ascend to a Higher Plane of Existence and happily travel the universe with Heather forevermore.

Bill is Susan's daughter and therefore the Doctor's great-grandchild.
There seem to be a lot of references to Susan in "The Pilot", and the Doctor even looks at Susan's picture when she asks why he noticed her. There's also the fact that the Doctor knew Bill's mother according to the picture she found, and it's possible that her mother is just Susan regenerated.
  • If Susan is Bill's mother, then Bill saying there's not many pictures of her mother, except those which were taken by the Doctor, makes a lot of sense too. As a Time Lady staying on Earth for some unknown reason, she could have been trying to lay low and not have wanted photos out and about which people she'd rather not have find her could potentially see and recognise her from.
    • Er, come again? This troper thought that Bill's foster mother saying she "didn't know we had them" made it abundantly clear that the Doctor'd popped back in time, tracked down Bill's mum, took all those photos, and planted them in the back of a closet as an anonymous Christmas gift for Bill. She'd gotten him one, after all.
    • The fact that the Doctor is seen in a mirror in one of the pictures with a camera supports this theory.
      • This troper absolutely agrees too that this is how and why the Doctor decided to get those physical photos for Bill, but the original theory doesn't contradict that. It remains the case that Bill's mum didn't seem to like having her photo taking much outside of letting those ones be taken by him for some reason. Maybe he already knew her and maybe he literally told her why he wanted the photos, we'll have to see.
  • Susan has been a parent and raised children on Earth before ("before" for her at least, as it did happen in the 22nd century), so at the least we know she's not opposed to such a thing.
    • The Doctor also took a similar tutor approach to Alex, Susan's now-deceased son (in the Big Finish New Eighth Doctor Adventures), as he is with Bill. Back then he wanted his great-grandson to travel with him and learn all he could, before his untimely death. Now he's travelling with Bill and playing a mentor role to her, even wanting her to learn how to make tough choices (like in "Thin Ice") in regards to the planet she grew up on.
  • As far back as in "The Pilot" Bill has claimed to gave "remembered" phrases her mother said, such as about travelers and as the season has gone on even "spoken" to her. Time Lords are very psychic, having a semi Hive Mind of sorts. If Bill's mother is a Time Lord what Bill could be seeing/remembering/talking to psychic residue that she left behind, explaining why it's all in such great detail (down to the specific mannerisms and voice) considering Bill lost her mum at such a young age.
    • Bill can also pick up psychic messages and have them replay for years, as shown by "World Enough and Time", lending weight to the residue theory.
  • The same actress for Bill's mum has briefly been on the show before, as a Time Lord.
  • In "Knock Knock", the Doctor is visibly affected by Bill referring to him as her "granddad" and claims he is only old enough to be her father.
  • Along with numerous references to Susan, there have been parental themes throughout a few episodes, such as:
    • In "The Pilot", there's the references to Bill's own mum.
    • In "Smile", one of the child settlers goes off looking for his mum, whose true death/fate he didn't know about and wasn't told about at any point in the episode.
    • In "Thin Ice", the lives of some homeless children are improved when the Doctor lies about the identity of the boy's father, forging documents so people believe him to be the son of a Lord.
    • In "Knock Knock", there's numerous parenthood references, from the relationship of the Landlord and his mother (with her not even knowing she's his mother at first), the focus on a picture of Bill's mom again and the Landlord also mentioning leaving a charge behind in the world to the Doctor, which gets a reaction from him.
    • The picture of the mother again appears in "Oxygen", and the Doctor winds up losing his eyesight just to keep Bill alive, a significant sacrifice for any companion, and especially someone he's only known a few episodes.
    • In "The Lie of the Land" Bill's memory of her mum helps save the world.
    • In "Eaters of Light" Kar is first encountered mourning her dead parents before also righting the rest of the dead
    • In "World Enough and Time", Mr. Razor (aka Saxon!Master) tells Bill that she's like a mother (or aunt) to him, though it's a ploy to keep her trust
  • Also, Bill ends up at least partially Cyber-converted in "World Enough and Time". The villains might have it in for her specifically to completely break the Doctor's hearts by not just making a companion but his great-grandchild suffer. And given what happened to Alex...
  • Her being read as human could be explained even without going into fob-watches in that "humanness" seems to be usually very dominant, like it was with Alex who never noticed his own mixed heritage until he was directly told.
    • Either that or they were sent up specifically for Bill by the Master rather than being triggered by any "human detector" this time.
  • Her surviving long enough to have her heart replaced, with it being stated she wasn't quite dead yet hence why the hospital could "save" her. If she was completely human she should have died immediately, but Time Lords do have an established aversion to dying, even when regeneration is impossible their bodies keep trying to persist. That resilience could have been inherited.

The ship that leaked the fuel was a Cyberman vessel
The Heather-geyser's face on the "quarry planet" as the TARDIS dematerializes strongly resembles that of a Cyberman, especially a Mondasian Cyberman. This suggests that the Cybermen were looking for Missy — or vice versa? — and that Heather may appear along with them in the Season Finale.

Kezzia and Goodthing were the descendants of Rani Chandra
The two sisters were descendants of Rani, who we met in The Sarah Jane Adventures, who we know from "The Mad Woman in the Attic" goes on to have children. Not only would Goodthing manage to be the last awake member of the settlement standing for a bit, which reflects the determination of that bloodline, but she looks awfully like ancestor Gita doesn't she?

We'll see a version of the Vardy again
Likely not those exact ones from that settlement and likely not even in this season, but a swarm of microbots with that much deadly and constructive potential? If someone with malicious intentions got their hands on that sort of technology, they could end up showing up again as an enemy at some point.

    "Thin Ice" 
Something bad is going to happen to Nardole
Not only do Nardole and the person in the vault clearly not get on, but Nardole also said the occupant won't get out while he's still around. Could be some foreshadowing.
  • Jossed.

Nardole is a living Chekhov's Gun
It was revealed here that in the past he had to go on the run and change his face (he also mentions in a later episode that he "should go back to being blue) and he's revealed in the next episode to be over two centuries old. We don't know much about his past but it definitely seems to be eventful.

The exact way he is a Chekhov's Gun is, however, up for speculation. It could be that his past history itself will turn out to be important, or perhaps he will just turn out to be even more of a secret badass than is already known.

  • Jossed.

The miners work for a subsidiary of The Company from The Sun Makers.
Their bosses' policies regarding worker exploitation and expendability, and specifically their eagerness to charge for everything necessary for survival (whether as "expenses" or "taxes"), seem awfully familiar.

The Doctor could fly the TARDIS by memory
Blind pets navigate by memorizing the layout of their surroundings. The Doctor has been operating those controls for so long he knows excatly where every button, lever, and switch is, and doesn't need to see them any more than a blind cat needs to be able to see where the living room furniture is.
The Vault isn't the big reveal of the season
Too many people guessed who was in it and it was revealed too early on in the series for this to be the big twist. Although, what other twist/s may be in store are up for guessing!

The planet where Missy was being executed was Skaro.
The last time we saw Missy, the Doctor had given regeneration energy to the Meat Moss Daleks. The next time, she's being led to her death by a group of people who have heavy disregard for other forms of life — kind of like the Daleks. Since the Doctor knew what Davros was attempting, it's possible that he gave the sewer Daleks enough regeneration energy to restore them to humanoid form, but not enough to make them Time Lord hybrids or eliminate their conditioning.
  • Unlikely. The residents of the planet were Human Aliens, and Skaro is a war-torn hellhole, while the executioners' planet looks Earthlike from space.

The random numbers weren't really random.
As pointed out by Artistic License – Engineering, computers aren't that bad at random number generation (The weakness is that after enough numbers are generated a pattern begins to develop, not that they always pick the same numbers) but what if they weren't truly random?

The Christian scholars who first discovered the truth were affected by a glitch which made them aware of their true nature. They then reproduced this glitch as the Veritas and the string of numbers within. Anyone who interacts with the Veritas directly or indirectly (like when the CERN scientist makes Bill & Nardole take "The Shadow Test.") becomes corrupted by the glitch. Now they cannot help but recite that string of numbers, because their programming has been overwritten!

The Veritas is actually a virus inserted into the "game" by those scholars, manifesting as a book. This is why it has such a strong effect on those who read it. The Prophets try to seize the book so they can locate the source of the infection and delete it.

The program was a failsafe set up by Missy to get herself free.
There is no legitimate reason why a race of aliens seeking to conquer the world would want their simulation to realize that it was a simulation. The Veritas would serve no function save distraction in the program. Unless, the whole point of the Veritas was to let the simulated individuals know that it was a simulation, drawing in the simulated Doctor, who then contacts the real Doctor. The Monks could have terminated their Doctor program at any point before he sent his e-mail to The Doctor IRL. And upon learning a massive alien threat was coming, The Doctor turns to ask Missy for help. Just as she was counting on him to do!

The Monks are servants of the Great Intelligence
Rested and ready, and having created a variety of bizarre servants before, the Great Intelligence has come up with a plan a Clara-echo can't undo — she would be brainwashed along with everyone else!

The simulation was based on Time Lord technology
The Time Lords'have had highly advanced matrix technology they've used to upload billions of real dead people. They'd likely be capable of running/creating a simulation like this with billions of just copies who only think they're real.The technology could have been swiped by someone malevolent.
  • Alternatively, corrupt Time Lords — there are so many of them! — are using the technology to conquer Earth and from there the universe, having grown tired of hiding at the end of time. Perhaps the void the Doctor left at the top of Time Lord government was filled by a would-be successor to Rassilon. Moreover, this would tie into the Doctor facing up to the consequences of his actions, as he has to stop a threat he inadvertently paved the way for. The Monks might be horribly corrupted Time Lords, or perhaps a lesser race promised power if they enslave humanity for the Time Lords.

Missy has a plan ready to go
Knowing Missy, she'll be prepared and the second she's out of the vault there'll be a plan of hers ready to go.
  • She may even have a plan already in-motion.

The U.S. President, unlike most people who read the Veritas translation, was murdered outright by the Monks.
The other people who killed themselves upon realizing that they weren't "real" did so either to free themselves from the travesty of life that is the simulation, or to disrupt the simulation itself. For most people, removing themselves individually was all they could do, but the President could presumably have done much more to disrupt the sim-world and/or free as many sim-people as possible: he could've deliberately kicked off a nuclear war inside the simulation, thus rendering it useless and freeing everybody at once. Rather than risk him taking such a drastic action, the Monks stepped through the portal into the White House, shot the man as soon as he'd finished reading, and made it look like another suicide.

Missy survived the execution, but did lose her ability to regenerate as planned.
The head executioner told the Doctor that their method of executing a Time Lord would stop both her hearts and all three brainstems, and would also permanently destroy her ability to regenerate. The Doctor was able to keep the device from killing Missy, but what if he wasn't able to stop all of its effects? Or possibly chose not to? Only having one life to live might make Missy more introspective, to have more sympathy for shorter-lived people. It also would give the Doctor a stronger threat to hold over her — she's seen him decide to kill her before, after all, and he would have if it weren't for the Brigadier beating him to it!

Time Lords aren't that hard to come by.
The planet of executioners (apparently it's named Carnathon) contacted Gallifrey to look for a Time Lord to kill Missy. Gallifrey referred Carnathon to the Doctor because they want the Doctor to spend the next thousand years in one place guarding her body rather than running around the universe causing trouble.

    "The Pyramid at the End of the World" 
The Monks are responsible for the state of near-war the world is in at the beginning
Okay, so this episode begins with the American, Russian and Chinese armies ready to go to war with each other, which is only delayed by the sudden appearance of the Monks' pyramid. They offer to save the world from its imminent destruction if humans willingly become their slaves — although not in those precise words. Given what "Extremis" reveals about how long they've been planning, it's extremely plausible that they manipulated the governments of Earth into this situation where they're nearly at the breaking point and the whole planet is in a panic specifically to make it more likely that humanity, driven to desperation, would be more likely to accept their offer.
  • Jossed. The situation with the armies isn't as tense as the trailers made it out to be, and isn't the real threat anyways.

The Monks are responsible for the situation that led to the creation of the killer bacteria
The Monks tweaked a few things, arranging for the one scientist's reading glasses to be broken and the other to be hungover, so that the killer bacteria would be created. See, from their perspective it doesn't matter whether the threat is the bacteria, or the Doctor in danger of dying while trying to stop the bacteria because of his blindness, either way they get what they want.

The Doctor's blindness, and Bill's ignorance of it, was what the Monks were depending on to get permission the entire time
It didn't matter what kind of threat was imminent, because thanks to their simulations they knew that the Doctor was blind, Bill was ignorant of it and that his blindness would make it more likely that he would get himself in lethal danger trying to save the day. They knew, thanks to their simulations, that they would be able to get Bill to agree to their offer so the Doctor would be saved, regardless what else was going on.

The Pyramid was a TARDIS, belonging either to Missy or to the previously exiled Time Lords
As Bill surmised, it looked like a pyramid, but it appeared overnight, so it had to be advanced alien tech. Something that can look like anything, appear out of nowhere, has psychic circuitry, and a computer program capable of calculating/prognosticating future Earth events based on observation? This sounds very much like a TARDIS, and likely a more advanced model than The Doctor's own "museum piece" Type-40. In addition, the way it stopped the bomber and the submarine? Not dissimilar to the Time-Stop we saw Missy use in "The Magician's Apprentice". Possibly a more advanced version on a more advanced TARDIS. And we haven't seen Missy/The Master with a TARDIS of his/her own since the return to the series. What would have happened to the one The Master utilized in the classic series?
  • Looking Jossed in that the pyramid ship apparently always looks like one, suggesting it has noting like a chameleon circuit. In "The Lie of the Land", it is simply relocated to London as is.

The Monks needed Bill's consent specifically, to allow them to control the Doctor.
As pointed out elsewhere, if the Monks just needed someone's love charged by fear of loss, why not show the UN secretary general or the soldiers their loved ones dying in the catastrophe and use their love of their families? Maybe it's because they specifically need love of the Doctor in order to control him? "The Lie of the Land" shows that the Doctor has become a Propaganda Machine, but why do they need propaganda if they have the entire planet under mind-control? Perhaps the Doctor is the medium through which they control the world... somehow, and this is why he needs to be "killed" to break it.
  • The Monks told the humans that a "link" would be made as soon as consent was given. In the trailer for "The Lie of the Land", Missy says that the person who "opened the door" to the Monks is the one that must be killed. While that would seem to be Bill, because she gave consent, the Doctor and his psychic abilities would make him an ideal medium for something involving mind control: The actual "link" between them and humanity, allowing more of their kind to come to the planet. In fact, it hasn't been established where the Monks came from; perhaps his brainpower will open a dimensional portal wider or some such. In any case, with the power they now have to brainwash him, implied in the final line of "Pyramid" — "Now see our world" — they can make him believe he is acting of his own free will and for the greater good, and consent to being their tool.
  • This is looking jossed, as the Doctor was only pretending to be brainwashed in an attempt to earn the Monks' trust so he could undermine them. They never controlled him to start with.

     "The Lie of the Land" 
It's Missy who raises the possibility of shooting the Doctor
Missy's a Time Lord too and while Bill may not know it won't permanently kill him and that he'll just regenerate (or usually should as it's unlikely to actually happen this time), Missy certainly will. She may be hoping to use the time a post-regenerated Doctor would spend disorientated to slip away too.
  • Jossed — Missy doesn't appear in the episode until after the shooting.

Missy will slightly enjoy the Doctor being brainwashed
One of the first things Missy tried to do in this incarnation in regards to the Doctor was to try convince him they were alike. While he may be brainwashed she may get some joy in getting to see him technically being evil.
  • Jossed: The Doctor was never brainwashed to begin with, he was faking it.

All three of the episodes are simulations, not just Extremis.
The Monks do not have reality-altering powers, nor any powers at all outside of being really good programmers. Anything they do is simply a result of altering the program, including taking control of the planes and fixing the Doctor's eyes.

The first simulation (seen in Extremis) failed because of the Veritas "glitch". The simulated-Doctor did not get a message to the outside, but instead to the next simulation which was identical to the last except for the Veritas being deleted by the Monks. The second simulation ended in their victory via Bill asking them to restore the Doctor's eyes, which was most likely the first simulation that did.

The simulation is altered so that the Monks rule and the Doctor is Brainwashed and Crazy, but even then the Doctor will find some way to counter them in the end. The Doctor will wonder just how the Monks accomplish the things they do, and have a suspicious feeling that he's not real... which he'll confirm after taking the "shadow test" and failing. The Monks will realize that there's no way they can win against the Doctor, ever, and abandon their plans for taking over the Earth and shut down all the simulations. Meanwhile, the real Doctor (who is still blind), Bill and Nardole will have no idea about anything that happened, and Missy will still be locked in the Vault.

  • Alternatively, Sim-Doctor 2.0 being shot and forced to regenerate will actually destroy their simulation. If the simulations are good enough they can email the real world, something causing the heart of their conquest to effectively "go nuclear" could be devastating.
  • Working against this idea is that much of the fanbase will be really angry if most of the events of the last three episodes and any Character Development for the regulars were All Just a Dream, as it were. It would also be a disservice to Bill to have her A Day in the Limelight episode turn out not to be real. Also, the Doctor does not appear to be blind in the final four episodes of the season from promo stills and the Series 10 trailers — he isn't wearing the sonic sunglasses in any of them, even when he goes to places like Mars or fights Cybermen. As he does not have any means of curing his eyesight in the "real" world, how is that possible unless the events of these episodes are real?
    • Unless Oxygen was also a simulation, albeit the Doctor went blind saving Bill. One outcome of this episode might be the Doctor subconsciously sending himself a message (somehow) to prevent that from happening, and then we'll get a heavily abridged version of the "real" episode where everything is identical only the Doctor does indeed regain his sight at the end.
  • Jossed: At the end of "The Lie of the Land", it's still six months after the Monks' invasion, although most of Earth has been given Laser-Guided Amnesia of their rule.

The promotional materials for this episode are lying about Bill shooting the Doctor dead
The very last shots (as it were) of the Next Time trailer show Bill shooting the Brainwashed and Crazy Doctor, shortly after Missy's dialogue establishes that he has to die to break the Monks' hold on Earth. The synopsis claims she "just might have to kill her best friend", with Missy clucking her tongue about the Doctor not getting a happy ending. The scenes of the regeneration come from this sequence. But that is a lot of stuff for official promo materials to spoil. There is a chance that Trailers Always Lie again and this is all misdirection via Imagine Spots, etc., and the characters find an alternate way to save the world.
  • Confirmed — it transpires that the gun was loaded with blanks, as the scene was actually a Secret Test of Character for Bill.

The Twelfth Doctor's "regeneration" activates a Timey-Wimey Ball to undo the events of this episode and "The Pyramid at the End of the World"
If the Doctor, Bill, and Nardole are to keep going on wacky adventures for the remainder of the season (all three have been confirmed for "The Empress of Mars" at least) and not be depressed/traumatized over Bill shooting the Doctor dead and all, then that can't have actually happened. The Doctor would be the only one who remembers any of this, going back to the events of "Extremis". While he would still be blind, perhaps he finally figures out a way to fix it in time for "The Empress of Mars", in which he doesn't wear the sonic sunglasses.
  • Alternatively, because he quasi-regenerates and undoes the events of these episodes, he also gets his sight restored as a happy side effect.
  • Or with the Doctor regenerating it could go back to the end of Pyramid at the End of the World instead of before, just after the Doctor's sight was restored and just before the monks took control/altered reality. That could also explain why he still has his sight even after a reset.
  • Jossed — it's only fifteen minutes into the episode, and is actually part of a Secret Test of Character.

The Twelfth Doctor is a case of Pretend to Be Brainwashed
The synopses and trailers suggest that the Doctor is Brainwashed and Crazy thanks to the Monks (given that Bill has to make him "see the truth"; it would also carry on from the last lines of "Pyramid"), but it's not definitively stated. This leaves two other potential options: Either he is Not Brainwashed and decided to do a Face–Heel Turn, which would be a huge violation of his character (and especially his arc this season), or he is faking it to find a way to destroy the Monks from within, given that he appears to have a high place in their inner circle as their Propaganda Machine. He has a mighty brain, after all, and might be able to resist the Monks' Reality Warper powers. On the other hand, they were powerful enough to restore his sight, and the theme of the importance of truth/honesty running through Series 10 would be derailed if he saves everyone through deceit — and right after his unwillingness to be honest with Bill led to tragedy in the previous episode, too.
  • Confirmed — he was attempting to worm his way into the Monks' trust to try and undermine them. This is revealed fifteen minutes into the episode.

The Monks are actually (fill-in-the-blank) in a different form
Nothing has been revealed about where the Monks came from, what they actually want out of enslaved humans, and so forth. They are incredibly powerful and have knowledge of all that has ever happened on Earth, and know that the Doctor is their greatest opponent. They have a spaceship disguised as a pyramid. Could it be they are not an original race but a different form of an established one? Candidates include...
  • Mondasian Cybermen: Their way of speaking is similar to theirs — sound comes from their mouths, but they do not move. Given that this particular "model" of Cybermen has been confirmed as being central to the Season Finale, perhaps the Monks are related to them in some way.
  • The Trickster: And the Arch-Enemy of The Sarah Jane Adventures brought his friends this time! The Monks' Reality Warper powers are very similar to his.
  • Time Lords: Specifically ones who have no regenerations left. The Master, at the end of his original cycle of lives, was virtually a walking cadaver before he took over Tremas and also wore a robe. Perhaps these dying Time Lords intend to take over the bodies of innocent humans. Bonus points if their leader turns out to be the exiled Rassilon.

If there is a reset something important will be forgotten.
Going off earlier theories that there will be a reset and that most bar perhaps the Doctor will forget the events.If this is the case, then this will result in something plot-important, perhaps even a reveal that occured in the episode, being forgotten.

Everyone but the heroes will get Laser-Guided Amnesia at the end.
Basically, when the Monks are defeated, the Reset Button will be pushed, but not temporally. It will still be six months later, but everyone on Earth won't ever remember the Monks' conquest except for the main characters, and maybe a few others. The time will still have passed, but this is one alien invasion that won't go in the history books.
  • Confirmed — when the Monks were forced to flee, they made everyone except Our Heroes forget their rule, and it is still six months later.

Missy's faking reforming
She's playing the Doctor, the Master has done many horrible things for the sake of victory and/or preservation so playing along with the Doctor trying to reform her if it helped her get something she wanted us very like her.Her crying at the end showing apparent remorse for her victims is due to how she earlier in the episode bragged about shoving a child in a volcano and callously suggested rendering Bill brain dead which got a backlash from the Doctor. She's realized this has set her "reforming" act back and is now playing it up for all its with to get the plan back on track.She has not changed one bit.
  • Quite likely, considering it's already been said that Missy "does something horrible" in the finale.
    • Jossed by "The Doctor Falls". The "something horrible" things she does in the finale, she does to her previous incarnation, rejecting the Saxon-Master's evil by stabbing him in the back.

The Monks got cocky
And that's why they were defeated so easily. They weren't expecting any proper resistance as they almost never really face any so they didn't prepare for it.

     "Empress of Mars" 
The Ice Warriors and Victorians come to a stalemate
The Ice Warriors start winning like seen in the trailer, but eventually lose that advantage and as things go on nobody will seem like they have a good chance at winning.
  • Jossed — They come to a truce instead.

The Doctor will turn against the Victorian soldiers
He won't necessarily join the Ice Warriors, but the Doctor is not a fan of genocide and if the Victorian soldiers go too far with their attack on the hive he will move to try put a stop to it.
  • Jossed — He realizes he has to Take a Third Option and threatens to destroy everyone (including himself) if they don't stop fighting instead.

We'll get a Saxon cameo
There's talk of a possible cameo of a popular character this episode. Perhaps he's it?
  • Jossed — Instead, Missy has a surprise minor role in the episode, and there's also a cameo by Alpha Centauri (of the Peladon serials of the Third Doctor era) in the denouement.

The reason why Missy asks the Doctor if he is alright at the end of the episode is because she knows that he is delaying a regeneration.
When Bill shot the Doctor in the last episode, maybe the bullets fired weren't blanks (as shown by one of the Monk guards forgetting to change his bullets into blanks for the Doctor's Secret Test of Character), and therefore, the regeneration seen there may have been only the healing section, and he is holding off changing his appearance.

Something else is wrong with the Doctor that only Missy could pick up on
Either as she's a Time Lord or because of how long they've known each other. No obvious, external wound that someone else could pick up on, but something serious enough that it's going to come up again.

Missy deliberately caused the TARDIS to come back
She wanted a chance to pull a stunt where she comes to help the Doctor before oh so nobly letting herself be locked up again, in a stunt to gain his trust. If he sees her apparently happy to leave the vault and help him he may eventually be inclined to let her do so more often. So Missy orchestrated the chance to do so. She's piloted TARDISes before and would likely know how to pull such a stunt. Adding to that, she did not sound surprised at all when Nardole arrived to ask for help and immediately suggested being let out to provide it.

The Ice Queen first thought Bill was boss of the humans
Females seem to lead the hive with Ice Warriors, so she might have asked Bill's opinion as she assumed that, since Bill was the only female of the group present, she held a high rank over them.

    "The Eaters of Light" 
The story starts as a Breather Episode, but something important happens near the end
It seems like a breather episode but is far too close to the finale to be just that. It's likely something very significant will happen towards the end.
  • Given that "Empress of Mars" unexpectedly managed to further the Vault Story Arc, this is looking likely — probably when the Doctor and company return to the present.
  • Jossed. While the last few minutes are given over to the Doctor and Missy pondering where their relationship is going, the actual denouement of the plot is self-contained, making it more or less a Breather Episode with a Bittersweet Ending.
    • Well, arguably Missy being revealed to now be allowed to be traveling with the Doctor could count as something pretty important happening near the end, especially as it will directly have a huge contribution to the next arc.

Bill ends up separated from the Doctor after trying to help a soldier
She seems to be alone with just a Roman in the trailer, so she at least gets separated from the Doctor at some point.
  • Jossed: She and the Doctor split up as the story begins, and she encounters the soldier while on the run from Kar.

    "World Enough and Time" 
Bill's death, teased in the promo materials, isn't a death but is a trap for the Doctor
The Next Time trailer and official synopsis suggest Bill is the person the Doctor pledged to protect (she asks him to promise she won't be killed) who ends up dead when Missy's attempt to be the Doctor on the spaceship goes horribly wrong, which would be a heartbreaking experience for him and something he'd feel he Must Make Amends for — by finding a way to undo it, given the ship has Time Dilation going for it — since it was his idea to let Missy be him for a day. But after the incredibly misleading promo materials for "The Lie of the Land" and Series 10 in general, Never Trust a Trailer — especially when there's more than one Master out and about. It could be that the whole business of Bill "dying" is actually a way to entrap him on somebody's part. Combine that with the shot of her in what appears to be a hospital ward, and she's in plenty of danger, but not necessarily in the grave.
  • The BBC America promo reveals she is doomed to become a Mondasian Cyberman, getting at least partially converted by the time the Doctor reaches her. In fact, there are few official photos of her in the publicity stills...but one has the Doctor is looking upon a Cyberman with horror and concern. Turns out, it's a full conversion, and possibly a trap by the Saxon Master to ensure Missy will decide Then Let Me Be Evil when the Doctor finds out and is broken and enraged.

The "hospital ward" is where people are converted into Cybermen
Mondas and Mondasian Cybermen are featured in the episode, and the fact that Bill, who is already speculated to get into serious danger this epic, ends up in a hospital where the other "patients" are all concealed seems suspicious.
  • The BBC America promo confirms this.

Bill will be Cyber-converted but her humanity will be restored in this episode or (more likely) "The Doctor Falls"
She's at least partially converted (the chest piece) in the trailers. The Doctor finding a way to undo this would be a Hope Spot:
  • He will use The Power of Love to encourage her to throw off the mental conditioning, and possibly her physical transformation as well
    • This could possibly involve Bill's birth mother
    • The main drawback of this method was that Bill's heart and surrounding tissues were blown out by Jorj. Can The Power of Love grow back those vital organs, or at least keep her alive enough for the Doctor to get some fresh parts?
  • He will find a way to reverse the process, perhaps using his sonic screwdriver to set up a little time bubble around her and then using his psychic abilities to turn back time for her
  • He'll turn the spaceship's Time Dilation issues to his and her advantage where they worked against them before
  • He will use regeneration energy. (Below, it's suggested that he'll try and fail to do this in the next episode, which is why he begins to regenerate himself.)
  • She will be fixed and end up in a more "normal/subtle" robot body like Nardole, as stated below.

Alternatively, she will be Cyber-converted and...
  • The Doctor accepts her as she is and she becomes a bodyguard and muscle for him in "The Doctor Falls", staying on as a companion afterward for at least the Christmas Episode and maybe Series 11. Helping her be a "good" Cyberman in touch with her emotions, possibly finding a way to redeem the entire race in the process, would be a fascinating Story Arc.
    • On the other hand, the Doctor probably doesn't want people to run screaming from and/or shoot at his companion all the time; Cybermen are feared across the universe after all.
  • Be Driven to Suicide when there's nothing the Doctor can do for her, but not without telling him not to blame himself for her fate
  • Make a Heroic Sacrifice to save the Doctor, ala Danny Pink in "Death in Heaven"
  • Slay one or both Masters for the Doctor, ala Cyber-Brigadier in the same episode
  • Lead the other Mondasian Cybermen in a battle to stop the Cybus and "Nightmare in Silver"-generation Cybermen, as well as the two Masters
  • The Doctor will Mercy Kill her and end her suffering
  • The Doctor will transfer her consciousness to a more suitable robot or clone body so she can live a quasi-normal life (hey, he fixed Nardole up well enough)
  • The Heather Creature will return and, as the Doctor nods and looks on with tears in his eyes, liberate Bill's soul from her Cyber-body, whereupon they are happily reunited and Ascend to a Higher Plane of Existence — traveling the universe together at last
    • Confirmed. Heather does indeed liberate Bill from her Cyber-converted body and they travel the universe together.
  • "The Doctor Falls" turns out not to be about the Doctor fighting the other Cybermen and Masters but his trying to save Bill in a more optimistic version of "Hell Bent"
    • Unlikely with the news that the Doctor has to protect the remaining humans on the ship from being Cyber-converted in that story; it would look bad for him to choose to Always Save the Girl (again) instead of saving a Bus Full of Innocents
      • Both civillians are saved perhaps? The Christmas special is said to be optimistic after all so an overall good season ending would help set that tone.

The Doctor promised Bill's mum to protect her daughter
Someone the Doctor is pledged to protect apparently suffers a bad fate. It's seeming to be Bill so far, but it's not been shown the Doctor pledging to anyone else to protect her as he did with Missy. Even the above identity theories aside, we canonically do know he met and befriended her mother at least to take the photos. Perhaps something was said during that meeting.
  • Unconfirmed. If he did, there's no mention of it in this episode.

We're going to see some flirting between the Masters
Because the video of them dancing looks like it's heading that way and both Missy and Saxon Master seem egotistical enough to do such a thing.
  • Confirmed: Saxon does, indeed, try to hit on Missy in "The Doctor Falls". She shuts him down.

He promised directly to whoever suffers the horrible fate to protect them
He didn't make any oath to anyone else, he just promised to them they'd be alright and then they weren't.
  • Confirmed. He cannot promise Bill she will not be killed, but he does tell her he will protect her "Within reason." Sadly, one can argue that he did...and it wasn't enough.

Something happens to Nardole too
Bill is notably on her on her own in the hospital in the trailer, meaning Nardole is either alone with Missy or not with anyone. What happened to him?
  • Jossed. Publicity photos have Nardole and the Doctor together by the time they get to the hospital ward Bill ends up in and indeed he survives. It's just that the Character Focus of this episode means Nardole doesn't have much to do. Maybe next week?

When they first meet, Simm Master thinks Missy is the Doctor
Missy is going around playing hero with companions and outright calling herself the Doctor. It's easily a conclusion that could be arrived at by someone familiar with the concept of regeneration.
  • Jossed, because Saxon is disguised as Mr. Razor at the time and she thinks he's an ordinary person.

Bill is not the one on the chopping block
Sure she's in huge danger and may even get partially Cyber-converted from the look of the trailer. But other than perhaps taking some damage she survives, the trailer is a deliberate misdirection trying to make us think it'll be Bill when reality it's someone else who's on the chopping block and going to be even worse off by the end of the episode — perhaps even dead.
  • There aren't many characters in the cast list for this one, and the significant ones (the two Masters, Nardole, and the Doctor) are all appearing in "The Doctor Falls". While Bill is set to be in that episode as well and Pearl Mackie is listed as playing her, she might only appear in spirit whether she's dead or Cyber-converted.
  • Jossed. She is shot through the chest and ultimately converted into a Cyberman, and unless this can be reversed or otherwise changed in "The Doctor Falls", she'll probably have to have a Mercy Kill or Heroic Sacrifice.

There was another Master between Simm and Missy
This episode will show the regeneration.
  • Jossed as far as showing the regneration goes. Whether there was another Master between them remains an open question. Simm's Master seems to assume he'll regenerate into Missy, but he (and we) don't actually know whether he does.

The Master caused the ship to near a black hole
Not noticing you are nearing a black hole until you're able to be pulled close enough to be that badly impacted by time dilation and barely able to reverse from it, is a huge mistake especially as the pilots should be well trained.

Perhaps there was deliberate sabotage to cause that by the Master for the sake of his plan.

Missy is just playing along with her past self
Even if she was faking reforming, that reveal of her "true colours" was far too quick on her behalf. She does not intend to stay on his side.

Missy will become the Good Counterpart of the Valeyard.
Missy doesn't clarify if she's the next Master after Harold Saxon, and doesn't even seem sure of it herself. If they were to do the unthinkable and have Missy Killed Of For Real or retire her as a villain, the Master could still come back as many times as he wants as a Master between Saxon and Missy, meaning Missy's arc is still unchanged. Rather than reverting to a villain or staying dead, Missy will end up regenerating somehow(maybe Saxon was lying that it would stop that, or she has some get out of death card) and complete her Heel–Face Turn while her younger self will still show up evil as ever. Basically, she's a reverse Valeyard, being a heroic future version of a villain. And like the Valeyard, this set up will allow an evil and good version of the same person to be active at the same time as long as people want. It would also give the Doctor a great ally against the Valeyard should he show up again.