Recap / Doctor Who 2017CS "Twice Upon a Time"

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Twice Upon a Time

"Can't I ever have peace? Can't I rest?"^note From left to right: Bill Potts, The TARDIS, the Doctor and the Doctor. Not pictured: A captain and the Doctor.

^{Click here to see the Radio Times magazine poster for this episode:}
"What happens now, where I go now, it has be alone."

Written by Steven Moffat and Chris Chibnall^note Uncredited
Directed by Rachel Talalay
Air date: 25 December 2017

Twelfth Doctor: Why are you trying not to regenerate?
First Doctor: I have the courage and the right to live and die as myself.
Twelfth Doctor: Too late, it's started. A few minutes ago, you were weak as a kitten, right? Now you're fine. We're in a state of grace, both of us, but it won't last long. We have a choice. Either we change and go on, or we die as we are.

The one where Twelve plus One equals Thirteen.

---

"Once Upon a Time, the Doctor refused to regenerate... twice."

"Previously on Doctor Who... 709 episodes ago", the First Doctor was in the midst of a confrontation with a bizarre new race of cyborgs, the Cybermen of Mondas, at an Antarctic military base and his old body was wearing a bit thin. Realizing he would soon be regenerating and terrified of what this would mean for his future, he wandered off into the Antarctic snow, far from his companions Ben and Polly.

Previously on Doctor Who... one episode ago, thirteen lives and a new regeneration cycle later, the Twelfth Doctor stumbled out into the Antarctic wastes and barely managed to put off his regeneration yet again. He had been barely saved from his final death in a battle with the Cybermen on a gigantic Mondasian colony ship, knowing Nardole would be looking after the colonists who were taken to safety. But he also believed his beloved companion Bill Potts to have died in a Heroic Sacrifice as one of those Cybermen. And his childhood friend turned nemesis and fellow Time Lady Missy (the Master) seems to have forsaken a Heel–Face Turn after he spent decades trying to rehabilitate her. At this point, the Doctor was tired of changing — tired of life itself. After everything he's gone through in this incarnation, Twelve has hit his breaking point and just wants to die permanently. So the TARDIS brought him to this familiar snowy waste to prove a point...

And thus these two Doctors cross paths. And then time freezes, a British army captain (Mark Gatiss) from the First World War appears in their midst, and a mysterious Glass Woman appears after that...

The Glass Woman is part of the Testimony, a mysterious construct that is kidnapping humans throughout time and space — taking them in the final moment of their lives to download their memories before returning them to their fates, and capable of creating avatars of these people from said memories. The Captain is just one of their latest subjects, and the Testimony insists on returning him to his proper time and death. The Doctors have something to say about all this kidnapping and are determined to figure out what the Testimony's grand design is; accompanied by an avatar of Bill Potts herself, they and the Captain escape to find answers.

Is there really hope for the Captain? Is a person truly the sum of their memories? What will it take to convince the original Doctor to embrace a future that will be marked by violence and sorrow? What will it take to convince his later self to keep going after that future has become the past? And with all the lessons they learned in this life, what kind of person will the Twelfth Doctor become after this adventure?

---

The 2017 Christmas special is the End of an Age in many ways. Out of several milestones, this episode serves as:

• Moffat's final Doctor Who script and final work as showrunner after eight years, with Chris Chibnall taking over for Series 11 to Series 13.
• The final episode to be composed by Murray Gold until 2023, with him having been the series composer since the revival in 2005. He would be succeeded by Segun Akinola from 2018 to 2022.
• The final episode of the trilogy which started with "World Enough and Time" and "The Doctor Falls".
• The final episode for the Twelfth Doctor (Peter Capaldi) and the first episode for the Thirteenth Doctor (Jodie Whittaker), which also makes it the first regeneration of the Doctor that involves a gender change.
• The first multi-Doctor episode since "The Day of the Doctor", featuring David Bradley as the First Doctor.
• The first full-length multi-Doctor special (and the first of any length since the mini-episode "Time Crash") to team up an original series Doctor with a revival-era one onscreen;
• The first time in the revival era — and only the second time ever — that a previously-seen incarnation of the Doctor has been played by a replacement actor in a major, episode-long appearance, with David Bradley replacing the deceased Richard Hurndall from "The Five Doctors" after Hurndall himself replaced the first First Doctor, the deceased William Hartnell, for that one-off multi-Doctor story, giving One the odd distinction of being played by more actors than any other Doctor onscreen (the runner up being Six, played by both Colin Baker and a Fake Shemp-ing Sylvester McCoy).
• The second time the classic 1963-style TARDIS interior design appears in the revival era, after a slightly smaller version appeared in "Hell Bent".
• The final appearance of the "neon" console room, which was first seen in 2012's "The Snowmen" and was slightly remodeled in 2014's "Deep Breath". It is also the final appearance of the external TARDIS police box prop in use since 2010's "The Eleventh Hour".
• The last Christmas Episode of the revival era for six years (until 2023's "The Church on Ruby Road"), as during the Chris Chibnall era the annual holiday special was aired on New Year's Day instead.

Previews: Trailer 1, "Children in Need" Preview Clip, Trailer 2.

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Tropes:

• 13 Is Unlucky: The Thirteenth Doctor starts her debut with a real doozy of a Cliffhanger.
• The Air Not There: When time freezes, the falling snowflakes halt in place, but the invisible air molecules don't appear to since the Doctors and the Captain are able to move around and breathe without any problems.
• All There in the Manual:
  • Word of God stated the Captain to be the Brigadier's grandfather. According to Henry Lincoln and the Haisman estate (who own the character and publish the spin-off Lethbridge-Stewart series), the Captain was the Brig's great-uncle, and his brother Alastair is the Brigadier's grandfather. A compromise was agreed upon to solve the conflict, in the form of a free story which establishes, or at least strongly (and deliberately) implies, that the Captain is, in fact, both the Brigadier's great-uncle and his biological grandfather.
  • Paul Cornell's Novelization more clearly explains Bill Potts's fate and why her glass avatar cannot tell the Doctor what happened after Heather arrived: The Testimony edits Glass!Bill's memories so she can interact with the Twelfth Doctor as she did up until they separated on Floor 507, rather than have their interactions affected by spoilers. Glass!Bill does have all her memories restored later, after Testimony decides the Doctor is trustworthy: Bill and Heather, after spending time exploring the universe, went back to Earth to live as humans and grew old together. This relationship was so happy that Bill ultimately chose to die as a human, but on her deathbed told Heather she was free to return to her Pilot form if she wanted, and she did. This also easily fills in any What Happened to the Mouse? details regarding Bill's adoptive mum and other people in her life. The 2020 short "The Best of Times" (written by Moffat) adds more details about Bill's post-televised life; circa 2020 she and Heather are temporarily estranged due to the relationship difficulties that come with the latter having become bit of a know-it-all during the time she was more Pilot than human.
  • The Novelization and "The Best of Times" reveal Nardole too got a Surprisingly Happy Ending post-"The Doctor Falls": The former specifies that he lived to 728 as the leader of the solar farmers, successfully handling several additional Cybermen advances until all they had to deal with were "Cybermats every spring", and ending up married six times ("two of them at once"). Moreover, the Testimony was going to send him back when they realized he wasn't human, but he convinced/guilted them into letting his memories be harvested!
  • The novelization also states the ring the Twelfth Doctor wears from the denouement of "Deep Breath" to the moment of his regeneration into Thirteen is "his wedding ring", representing his relationship with River Song, whom he informally married in the Series 6 finale and previous incarnation. In fact, Twelve's relationship with River factors into why he would rather not regenerate: Having known something akin to human, romantic love with her (she's the key reason he'd rather not have One see the browser history!) and borne her loss makes him feel like he's lived a truly full life. When he decides to keep living, he also accepts that he can't stay as he is because of that feeling — (s)he needs to desire more again.
  • The Novelization also heavily suggests that the First Doctor's sexist remarks were made in jest solely to annoy the Twelfth Doctor. First doesn't seem to express such beliefs when talking to Bill on her own in the episode, backing this up somewhat.
• And Starring:
  • The billing of Pearl Mackie is presented this way in the first trailer.
  • In the episode proper, it's David Bradley who gets the "and" in the intro. The credits, naturally, end with "And introducing Jodie Whittaker as the Doctor."
• Armor-Piercing Question: Bill gets in a decent one when she asks why the Doctor left Gallifrey, enough to make the First Doctor stop and think:
  Bill: I don't mean what you ran away from. What were you running to?
  First Doctor: That's rather a good question.
  Bill: Questions are kinda my thing. How are you with answers?
• Astonishingly Appropriate Interruption
  Captain: But it's so... [Bigger on the Inside]
  First Doctor: Hideous!
• Arson, Murder, and Jaywalking: "Never be cruel. Never be cowardly. And never, ever eat pears!"
• Back for the Finale:
  • Pearl Mackie returns as Bill Potts... more specifically the memories of Bill Potts, which are really the sum of a person anyway.
  • Rusty the Dalek makes a very unexpected comeback.
  • Near the end of the episode, avatars of Clara and Nardole also briefly show up.
  • In a meta sense too, Murray Gold revisits many of his iconic pieces before stepping down as series composer. The Ninth Doctor's theme (commonly called the "Bad Wolf" theme and officially labeled "The Doctor's Theme"), "All the Strange, Strange Creatures" from the Tenth Doctor's era, the eponymous "Doomsday" theme, the Eleventh Doctor's theme "I Am the Doctor"/"The Majestic Tale", the Twelfth Doctor's theme "A Good Man?", and "The Shepherd's Boy" from "Heaven Sent" all make appearances here, alongside several other pieces that are subtlely strung out across the episode.
• Back To The Early Instalment: The special begins with footage from The Tenth Planet which then morphs into a recreation with David Bradley reenacting William Hartnell's portrayal of the First Doctor's last few scenes.
• Badass Boast: The First Doctor is rather bemused by Twelve doing this, as he's tipping off his opponent of his intentions before he carries them out.
• Badass in Distress:
  • The Twelfth Doctor is still dressed in his singed and torn clothes from his battle with his Cybermen, and his hair is a mess. More importantly, he's also actively trying to fight off his regeneration.
  • The episode ends with the Thirteenth Doctor literally tossed out of the TARDIS and cast into freefall.
• Being Good Sucks:
  • The First Doctor admits that he's baffled by how the universe maintains the Balance Between Good and Evil, and that evil ought to triumph constantly. Good requires things like loyalty, self-sacrifice and love, and is generally not a practical survival strategy.
  • The Twelfth Doctor, upon agreeing with the TARDIS that the universe does still need him, decides that regenerating into his next life and soldiering on won't kill anybody... except, of course, this particular incarnation.
• Berserk Button: Rusty tries to kill the Doctor for calling him a "good Dalek", once again replying that the Doctor is a much better one.
• Big Bad: The Doctor initially believes Testimony to be this but turns out to be mistaken.
• Bigger on the Inside: But of course. The Captain, this time. Once again, of course, the Doctor is expecting this:
  Twelve: You know, I thought it probably was. Glad it's not just me.
• Bilingual Bonus: The German soldier whom the Captain regretfully faces down, pistol to pistol, is also saying he doesn't want to kill his counterpart and pleading for Lethbridge-Stewart to just leave him there.
• Bookends:
  • The running trend continues as another incarnation of the Doctor dies as he was born: on Christmas.
  • Steven Moffat's tenure began with a Doctor who initially believed he had become a girl after his regeneration. Now, his tenure ends with the Doctor becoming a woman for real.
  • The first shot we ever see of the Twelfth Doctor in "The Day of the Doctor" is a closeup of his eyes, with fierce determination. The last shot we ever see of the Twelfth Doctor is his eyes, softened, relenting.
  • In The Time of the Doctor, one of the first things Twelve feels is pain in his kidneys. Here, one of the last things he feels is the same thing.
  • In Twelve's first episode, "Deep Breath", he felt hurt and rejected when Clara initially wouldn't recognize him as a new regeneration of "her" Doctor. In his last episode, it's Bill who feels that way when Twelve is reluctant to accept her as a legitimate manifestation of his young friend.
  • The First Doctor's first scene in the episode starts with original footage from "The Tenth Planet" with William Hartnell's performance, before transitioning into a recreation of the scene with David Bradley. His final scene begins with David Bradley setting the scene, before transitioning back into the original footage with Hartnell for the actual regeneration sequence.
  • As one showrunner leaves, the Doctor's regeneration is violent enough to wreck the interior of their predecessor's control room and the new incarnation, in the tattered clothes of their former self, ends up clinging on for dear life as the doors of the ship are knocked open and they nearly fall out. Except for one thing: Thirteen really falls out while Eleven managed to pull himself back in.
  • One for Moffat's onscreen tenure as a writer: As in "The Empty Child"/"The Doctor Dances", Everybody Lives — even though some must regenerate to do so.
    • Also, both episodes feature a largely benevolent antagonist whose villainous actions are largely accidental, in the nanogenes, and the testimony.
  • A throwaway reference in Moffat's first story written for the show to the weapon-factories of Villengard pays off twelve years later, as we finally get to see what Villengard looks like.
  • At the end of the previous episode, the Doctor tells himself to "let it go" as he starts to regenerate, refusing to change despite his own survival instinct. At the end of this one, he tells his current self, "I let you go," as he accepts the change that's coming at last.
  • On a similar note, Moffat's run began and ends on the heels of perfectly contrasting last words and a whole lot of Character Development in between:
    Ten: I don't want to go.
    Twelve: Doctor... I let you go.
  • Murray Gold's final episode (at the time) concludes with the Ninth Doctor's theme, which he created for Series 1, playing during the Thirteenth Doctor's first scene.
• Both Sides Have a Point: The Twelfth Doctor refuses to consider that Bill is the real Bill while she insists that she's the real deal. While it isn't Bill "in the flesh", proving the Doctor correct, it is the sum of her memories (and by implication, personality as well), which proves Bill right.
• Borrowed Catchphrase: After Twelve accidentally lets on that it is only the First World War (implying there will be more) he has to console the Captain with his wife's line of "Spoilers".
• Brain Uploading: The Testimony does this with humans' memories and by extension personalities and can download them into Glass People avatars.
• Brick Joke:
  • In the 2005 episode "The Doctor Dances", the Doctor mentions how he visited the weapon-factories of Villengard once, but they were destroyed (presumably because of him). In this episode, his twelfth incarnation finally travels back to Villengard, bringing things full circle.
  • Internal to the episode, the First Doctor finds the brandy stash in Twelve’s TARDIS, noting that some of it has gone missing. When he returns to his own stash and pours some of the version there, he notes “So that’s where it went.”
• The Bus Came Back:
  • As this story takes place during the events of "The Tenth Planet" for the First Doctor, Polly and Ben appear with him as The Cameo in the opening sequence. Later, the interior of his TARDIS as well as the 1966 exterior police box design appear in larger "roles".
  • Rusty, the "good" Dalek in "Into the Dalek" returns, having spent the intervening billions of years killing other Daleks who came to exterminate him. He also seems to despise the Doctor for making him into what he is and also tries to exterminate him as well (at first).
• Call-Back:
  • The Twelfth Doctor declares the Earth as being under his protection once more (as each of the new series Doctors have done at least once since the Tenth Doctor in "The Christmas Invasion") — much to his original self's confusion, as he doesn't think of himself as holding such duty.
  • One to Steven Moffat's first story for the Revival, as this story visits the ruins of Villengard, which was mentioned all the way back in 2005's "The Empty Child"/"The Doctor Dances". Oddly enough, there's no banana grove. Was Nine joking all along?
  • The First Doctor threatens Bill with a smacked bottom.
  • The Doctor keeps brandy in the TARDIS. Which explains where River got it from.
  • Bill laments that she's standing right in front of the Doctor and he can't see that she's real, echoing back to Twelve's first episode when he complained the same thing of Clara who couldn't reconcile him as being the same Doctor she'd known.
  • In "The Doctor's Wife", the TARDIS tells the Doctor she takes him where he needs to go, not where he wants to go. Here, she deliberately takes him to where his First Doctor is about to regenerate, rather than some quiet place to die for real. In the novelization, Twelve even explains the TARDIS's way of thinking to One in a direct reference to this episode.
  • The Twelfth Doctor again likens regeneration to a big lunch.
  • When the First Doctor is about to regenerate, a bit of "Vale Decem", the music that heralded the Tenth Doctor's departure, plays.
  • As the glass replicas of Bill and Nardole hug the Doctor together, Nardole says "cuddle".
  • Oh, look, the Doctor held back his regeneration until the last possible second again and now the TARDIS has been blasted all to hell and is falling out of the sky. Well, actually, the Doctor is the one falling out of the sky, this time. The TARDIS itself tosses her out and then dematerializes, mid-fireball.
  • The Novelization adds even more call backs, including the Doctors recalling their old teacher Borusa's wisdom "In hope you are at your weakest, in strength you are at your worst." Twelve realizes all of his lives beyond his first often forget the second part to their ultimate sorrow, and it has "become the most reliable part of his character." Twelve, embarrassed, ruefully notes that Borusa was ultimately a Hypocrite given his actions in "The Five Doctors". This exchange takes place shortly after the Testimony has revealed the grim side of the First Doctor's future lives to him, which in the book includes nods to the tragic ending of "The Waters of Mars" and the fates of Adric (killed), Donna Noble (Laser-Guided Amnesia and resultant loss of Character Development), and Bill Potts (Cyber-converted — though she got better of course). And Rusty comments to Twelve "You would make a good Time Lord" — which the Doctor sees as a much more hurtful comment than "You are a good Dalek."
• The Cameo: Ben, Polly, and the Mondasian Cybermen appear in the opening Previously on… sequence, but are absent from the rest of the episode — Mondas having been destroyed at the end of "The Tenth Planet", and time freezing before Ben and Polly catch up to One.
• Casting Gag: One is disappointed that he doesn't regenerate into someone physically younger when he thinks Twelve is next up, prompting Twelve to scream that he is younger. Peter Capaldi is older than William Hartnell was at the chronological time of his final story but younger than David Bradley, meaning they are both right from a certain point of view.
• Christmas Episode: The fourteenth and last in the franchise until 2023. It's also the third to double as a Grand Finale for an outgoing Doctor.
• Christmas Miracle: How the story ends on an Everybody Lives note (discounting the Doctors having to regenerate): The Twelfth Doctor is able to move the Captain's standoff a few hours ahead so it can be interrupted by a real life example of this trope, the Christmas Truce, which he explicitly describes to the First Doctor as "a human miracle".
• Chronic Hero Syndrome: The Twelfth Doctor finally decides to regenerate because, as the Testimony avatars and later the TARDIS remind him, the universe still needs his aid — the Doctor even notes to the TARDIS that they'll probably screw things up without him — and at hearts he cannot bear to turn his back on those in need.
• Cliffhanger: The episode ends with Thirteen flung out of the TARDIS as it's exploding, necessitating a new console room; wherever she lands will presumably be where she finds her new companions. Since where and/or when the TARDIS dematerializes to is unknown, the Doctor may or may not be stuck on Earth in The Present Day for a bit.
• Comically Missing the Point: When the Doctors and the Captain first enter Twelve's TARDIS, One thinks that it's his TARDIS, and he's been burgled upon seeing the revamped interior.
• Continuity Nod:
  • The First Doctor doesn't react well to the much-changed decor of his future self's console room.
  • Villengard, home of the weapons factories that the Doctor destroyed at some point in his lives according to the Ninth Doctor storyline "The Empty Child"/"The Doctor Dances", features in this episode. That two-parter was Moffat's first official Doctor Who script.
  • One is perplexed by Twelve using the Sonic Screwdriver, seemingly not knowing what a "sonic screwdriver" even is. This makes sense, as One never used a sonic during his run, the first use being done by Two in 1968. One relied on his trusty signet ring instead.
  • The Doctors and Bill end up in One's TARDIS — and in addition to the traditional roundels, one wall of it has the same hexagon design on its walls as the Curator's gallery in "The Day of the Doctor" did.
  • When the Twelfth Doctor realizes the Captain is confused and distressed by Twelve calling his war World War One, he tells him he can't explain matters further by using River Song's favorite warning — "Spoilers."
  • To "The Day of the Doctor".
    Twelfth Doctor: We do have one little advantage.
    First Doctor: What advantage?
    Twelfth Doctor: There's two of us.
  • When One and Twelve first enter Twelve's TARDIS and One is insisting he has no idea who Twelve is, Twelve tells him "I'd tell you to stop being an idiot, but I kinda know what's coming."
  • Twelve makes a comment to One about remembering where to park and that it's "going to come up a lot". The number of times the Doctor has forgotten where he parked, parked in a place that eventually becomes inaccessible, or parked in a place that results in him being separated from the TARDIS is astonishing. The Twelfth Doctor just ended up in this position in "World Enough and Time"/"The Doctor Falls" (the TARDIS couldn't travel from one end of the ship to the other, and he and his friends couldn't take the lifts back to it in the second half — had it not been for Heather, he'd never have been returned to it) and listing all the other times (that we know of) would take forever.
  • While he's dying, Twelve once again asks why he can't just rest.
  • As indicated during his pre-regeneration monologue, the Doctor still hates pears.
  • When Twelve regenerates, one of the first post-regeneration shots is of a ring slowly falling down the Doctor's (now) more slender fingers. When the First Doctor regenerated, Ben and Polly tried to confirm his identity by making him wear One's ring, which wouldn't fit Two's more slender fingers. Fittingly as both Doctors just had this adventure together.
  • The Testimony originate from New Earth, first introduced in the episode of that name back in 2006.
  • Once again, Twelve would rather nobody look into the browser history on his sonic sunglasses.
• Crucified Hero Shot: Twelve strikes this pose when he finally regenerates. It is appropriate for many reasons: he is kinda-sorta dying and reviving, he is doing it to continue saving people, and he does it despite acknowledging that more pain and sorrow is likely in store for him.
• Cryptic Background Reference: When the Glass Woman shows the first Doctor his future and lists off his nicknames, some of them have never been heard on the show before. Most of those are connected to things that have been depicted on the show (the Imp of the Pandorica, the Shadow of the Valeyard, the Beast of Trenzalore, the Butcher of Skull Moon), but "The Last Tree of Garsennon" is completely new.
• Death Seeker: The Twelfth Doctor, since he no longer has anything Worth Living For and does not want to keep living in different bodies with different personalities. At the very end, he decides helping others is Worth Living For in and of itself.
• Deliberate Values Dissonance: The First Doctor is sexist compared to the Twelfth — upon Bill and Twelve's reunion One suggests that she tidy up his later self's TARDIS. This reflects how much time, experience, and Character Development have passed between the two incarnations in-universe, and out-of-universe the roles and depictions of female characters, especially companions, in Doctor Who since the show launched in The '60s. It also prefigures the Doctor regenerating into a woman for the first time at the end of this story.
• Despair Event Horizon: The Twelfth Doctor has once again reached this point (the first time was when he temporarily became a Woobie, Destroyer of Worlds in "Hell Bent"), wanting to die for good if he cannot stay as he currently is, and the TARDIS has brought him to meet his previous self to bring him back from it and keep on living, along with convincing his first self to regenerate in the first place.
• Detonation Moon: The collateral damage from whatever destroyed the Weapon Forges of Villengard includes the moon overhead.
• Did I Mention It's Christmas?: As with all of the Twelfth Doctor's Christmas adventures after his first one, "Last Christmas", Christmas itself has only a minor part to play in the story. The Doctor takes the Captain back to the start of the Christmas Truce, which ensures that he survives a standoff which would have been lethal.
• Do Not Go Gentle: Neither Doctor wants to regenerate and suffer the Loss of Identity (a sort of death) that comes with it, and thus are fighting the impending change even if it means they have to die permanently. They wind up having one last adventure that ends in each accepting their transformation at last.
• Double Consciousness: It's clearer in the novelization, but Glass People have these when they are serving as avatars of the dead. Glass!Bill is confused as to why she cannot remember things past Heather's arrival and is desperate to convince the Tweflth Doctor she is Bill Potts, but at the same time she remains an extension of the Testimony (which has temporarily given her Laser-Guided Amnesia) and it is observing the Doctors and Captain carefully to see if the former can be trusted. Her Revealing Hug with the First Doctor has her switching from Bill's personality to speaking as the Testimony.
• Driving Question:
  • Why has the TARDIS brought the Twelfth Doctor to meet his original self?
  • What exactly are the "enchanted glass people" who can travel through and freeze time, what do they do to the innocents they kidnap, and why are they doing it?
• Dying Alone: Or rather regenerating alone; Twelve is alone in the TARDIS when he regenerates.
• Embarrassing Browser History: The Twelfth Doctor enjoys the sight of his Edwardian-looking past self wearing the sonic sunglasses...until his predecessor notices something called 'browser history'.
• The End of the Beginning: Twice over. Promotional copy for this episode even included "It's the end of an era. But the Doctor's journey is only just beginning."
  • The First Doctor is just The Doctor from his perspective at the beginning of the episode, and he does not want to regenerate. His choice to do so in the end, which involves accepting that he will be taking a more active role in protecting others and especially humanity, allows the entire rest of Doctor Who to unfold.
  • Between "World Enough and Time", "The Doctor Falls", and this episode, the Twelfth Doctor has his Final Battle and Heroic Sacrifice, has his Myth Arc with Missy wrapped up, and sees a few of the major loose ends of his tenure resolved as he bids his final farewells to those he loves (or at least their avatars). While he also goes into this episode wanting to just reach The End, he decides to regenerate after all — becoming a she in the process, which in a meta sense opens many new possibilities for the franchise.
• End of an Era: This episode marked the end of Steven Moffat's tenure as showrunner, as well as the last story to be scored by Murray Gold.
• Enemy Mine: The Doctor tells Rusty that he should help him because that will piss off the Daleks.
• Everybody Lives: Comes with No Antagonist, and even the Captain is eventually saved from his fate by the Doctor.
• Evil Plan: Only it's not. The Twelfth Doctor is rather flummoxed.
  "Oh, it's not an evil plan. I don't really know what to do when it isn't an evil plan."
• Explain, Explain... Oh, Crap!: When Bill first appears, Twelve asks how she can be here if she was a Cyberman last he saw her. Bill explains how Heather showed up and brought her back. Then the Doctor asks where Heather is. Bill doesn't have a good answer for that one, leading to the Doctor figuring out that she's a construct of the Testimony. The novelization explains that Glass!Bill's memories have been edited so she'll interact with the Doctor exactly as they did before they parted, though poor Glass!Bill initially doesn't realize this.
• Extremely Short Timespan: Events unfold over a few hours at most; given that the two Doctors are at regeneration's door, a longer adventure just isn't in the cards.
  • Taking "The Tenth Planet" into account, One's side of this story unfolds over a day or so in total, also falling under this trope. By comparison, Twelve's side — from first talking to Bill and Nardole about his plans for Missy in "World Enough and Time" to his finally regenerating — unfolds over a month or so.
• Face Death with Dignity: A major theme of this story.
  • The Captain is prepared to do this on the battlefield, and only becomes more determined to do so when he learns that's exactly how history records it. This is even in the face of the hope that he might escape his fate due to the Doctors. In the end, he doesn't have to die after all thanks to the Twelfth Doctor's timeframe shifting, but by that time the Testimony has given him Laser-Guided Amnesia of the events he undergoes out of time (he does stop short upon seeing Twelve among the people at the Christmas Truce, but that's all) and all he truly knows is that he was ready to die when a human miracle spared him.
  • The First Doctor is unwilling to regenerate and suffer the metaphorical death (Loss of Identity) that comes with it because he's afraid of his future as other selves, but after the Twelfth Doctor's example shows him the good he'll be able to do, he accepts and peacefully gets on with it.
  • The Twelfth Doctor is unwilling to regenerate because he's just tired of living and changing altogether due to Who Wants to Live Forever?, especially in the wake of "World Enough and Time"/"The Doctor Falls"'s events (and by extension, "Hell Bent"'s) reminding him he has no one who might be at his side forever. He invoked this trope when he defeated the Cybermen in "The Doctor Falls", in fact, and only Bill's Puddle-enhanced tears saved him from his permanent death. Although he is ready to embrace the end of everything at last for most of this story, he finally decides that he can't turn his back on a universe that he knows needs him, a motivation born of both ego and kindness. He still fits this trope in that he accepts the metaphorical death of regeneration to do so, just as One does.
  • The Novelization's explanation of Bill's post-"The Doctor Falls" life reveals that she and Heather ultimately decided to live and grow old together as humans after time spent exploring the universe and getting to know each other better. When Bill's once-more-mortal body wore out, she decided not to be turned back into a Pilot like Heather and thus rejuvenated and immortal, but rather allowed herself to die for good. However, she told Heather she should feel free to be a Pilot again, and Heather obliged. As Bill saw it, both of them were free of their old bodies, just in different ways. But at the same time she will not allow the Twelfth Doctor the same "luxury of mortality" for himself because she knows how much the universe needs him.
• Face Hugger: In a rare sight, A Dalek outside its casing attempts to exterminate the Captain, but it's soniced off by the Doctor.
• Failed a Spot Check:
  • The First Doctor fails to notice the snow has frozen in place until Twelve points it out.
  • Twelve is so focused on the Glass Woman being an artificial construct of the ship that he misses the fact that her face is asymmetrical, which would not be the case were the computer merely imitating a human. As One notes, she must be modeled after an actual human.
• Final Speech: The Twelfth Doctor gets one before he regenerates at last, addressed to his next self. Given that this Doctor was particularly good at speeches, this is fitting.
  The Doctor: Oh, there it is. Silly old universe. The more I save it, the more it needs saving. It's a treadmill. [the TARDIS makes argumentative noises] Yes, yes, I know they'll get it all wrong without me! [the TARDIS beeps in approval] Well, I suppose one more lifetime won't kill anyone... Well, except me... You wait a moment, Doctor! Let's get it right. I've got a few things to say to you. Basic stuff first. Never be cruel, never be cowardly. And never ever, ever eat pears! Remember, hate is always foolish and love is always wise. Always try to be nice, but never fail to be kind. Oh, and you mustn't tell anyone your name — no-one would understand it anyway. Except... [collapses to the floor and winches in pain] Except, children. Children can hear it, sometimes if their hearts are in the right place, and the stars are, too. Children can hear your name... [groans as he struggles to get back on his feet] But nobody else, nobody else, ever. [manages to stand up again] Laugh hard, run fast, be kind... [takes a moment to straighten his clothes a bit] Doctor, I let you go.
• Flanderization: The First Doctor, unlike in his original run of stories, is portrayed as straight-up sexist with regards to the role of female companions — an attitude Played for Laughs as the episode's Running Gag. This is an atypical example of the trope — it's downplayed as it involves a single appearance of a character who hasn't been seen for decades in anything more than stock footage and his character isn't completely defined by sexism. It's also justified as Moffat and company are poking fun at mores of The '60s as compared to those of The New '10s, and how societal changes have been reflected in the show, partially by way of setting up the Gender Bender regeneration of the Twelfth Doctor into the Thirteenth at the end of the story.
• Flashback with the Other Darrin: The events of "The Tenth Planet" are seen in the Previously on… sequence, this time with new actors playing the Doctor, Polly, and Ben.
• Future Me Scares Me: The First Doctor is upset to learn what he'll become and go through many regenerations down the line, starting when Twelve proves his identity to him via the glow of regeneration energy — for one thing, One thought he'd regenerate into someone younger-looking than Twelve. Much more seriously, finding out he'll be known as such things as "The Doctor of War" terrifies him, but The Testimony and later Twelve show him that he need not be afraid.
• Gender Bender: The Twelfth Doctor regenerates into a woman at the end.
• Glad I Thought of It: One points out that the Glass Woman has an asymmetrical face and thus must be based on a real person. Later, in One's TARDIS, Twelve brings up her face on a monitor and explains how he noticed that. One protests, so Twelve jokes how they're the same person.
• Good All Along:
  • The Doctor initially presumes the Testimony is some kind of nefarious plot, because that's the modus operandi of the show. Eventually he learns it's a future initiative meant to preserve the memories of the dead so they can be better remembered, and has only good intentions. Twelve is genuinely flummoxed.
  • In the Novelization it's explained that the Testimony initially doesn't know if the Doctor is good and means well in trying to save the Captain, given his reputation as the Doctor of War and so forth. This is why it allows the glass avatar of Bill Potts to follow them out of the ship, and her interactions with One and Twelve help convince it that the Doctor is good all along.
• Good Counterpart: The Testimony is this to the Nethersphere of Series 8 — where that storehouse of departed humans' consciousness was all a scheme to create a Cybermen army, the Testimony's collected memories allow the dead to be lovingly, respectfully remembered and even to live again as they were after a fashion. It's even referred to as "Heaven on New Earth".
• Good Is Impotent: The First Doctor thinks this, because the traits associated with 'good' seem to contradict those necessary for survival or success.
• Good Is Not Nice: Played with. As he's about to regenerate, the Doctor gives his future self some advice in the form of rules to live by. "Try to be nice" is the only one which is worded as optional, "but always be kind."
• Grand Finale:
  • This is the third and final part of the Twelfth Doctor's, the first two parts being "World Enough and Time" and "The Doctor Falls". It's also been confirmed as companion Bill Potts' final appearance (for now).
  • This is also a retroactive one for the First Doctor, seeing as for him it takes place after his first confrontation with the Cybermen but before he regenerates.
  • In a meta sense, much like "The End of Time" for Russell T Davies, this episode serves as the finale of Steven Moffat's tenure on the show.
• Hand Wave: The First Doctor's somewhat different appearance is suggested by Twelve to be an effect of his regeneration being unstable, so his face is "all over the place".
• Heroic Sacrifice: Both Doctors really, really don't want to accept regeneration. One is afraid of his future, and Twelve is simply tired after all he's been through in this incarnation alone, never mind the Loss of Identity issues. But each decides that it's better that they give up their current lives so that their successor(s) may exist and help others.
• Historical Person Punchline: Done with a person of in-universe significance; it's not until they're saying goodbye that the Doctor asks the Captain's name and learns that he's an ancestor of Brigadier Lethbridge-Stewart.
• History Repeats:
  • Once again, Steven Moffat bears witness to a Thirteenth Doctor who is female. Also fittingly serves as Bookends, as that was the first televised story he wrote for Doctor Who (though absolutely non-canon), and this one is his last (at least as showrunner).
  • Moffat's run began and ends on the same note: the Doctor regenerating and subsequently blowing up the interior of the TARDIS.
  • At the end of an emotional confrontation with one of his great enemies and after an ensuing Heroic Sacrifice, a bitter, cynical, middle-aged Doctor regenerates into a new, young incarnation with bright brown eyes and a charming smile. This change — marking the passing of the torch from a well-known veteran actor to a total dark horse — leaves fans uncertain, but mostly hopeful. Here we go again.
  • As in the first Twelfth Doctor Christmas Episode, "Last Christmas", he is reunited with his most recent companion not long after — at least from the Doctor's perspective — they seemed to have parted ways forever with neither knowing the truth about the other's situation.
  • Once again, the Doctor's regeneration story has the word "time" in its title.
  • Not to mention it has the Doctor angsting about regeneration on the last episode of a showrunner's tenure, even after his last incarnation was perfectly fine with regenerating and everyone knows it's going to happen.
  • Steven Moffat retroactively shakes up the established order of the regenerations yet again, this time targeting the circumstances behind a regeneration rather than pulling a cut-and-paste addition to the existing incarnations (though we still end up with a new one by the end). Moreover, the Doctors involved in the multi-Doctor adventure are both due to meet the end of their lives, mirroring how War, Ten, and Eleven were about to fare.
  • A Moffat script once again has people being pulled out of time at a moment where Time Stands Still for them, specifically in the final moments of their lives — just as happened with Clara in "Hell Bent". In that story, it was the work of the Time Lords and the desperate Doctor; here, it's the work of the Testimony.
  • Once again, the Doctor sees the first person to ever see that incarnation of him just before regeneration. This time, however, Clara isn't the last person Twelve sees; that would be Bill and Nardole going by the televised episode. In the Novelization, much the way Eleven had a vision of Amy Pond before he regenerated, Twelve has a vision of Thirteen.
• Hope Bringer: The Doctor being this is discussed. Bill asks the First Doctor why he stole the TARDIS, only to clarify that she wants to know what he stole it for, as opposed to what he was running from. The Doctor gives a speech about how evil has an inherent advantage yet never seems to succeed, and Bill points out that he can't see that the cause is himself.
  • In the Novelization Thirteen is this to Twelve. She is the very last person he sees, in his mind's eye, before he lets the Doctor go, and the sight fills him with hope.
• Hope Is Scary:
  • A Continuity Nod to the Twelfth Doctor and Missy's closing conversation in "The Eaters of Light" has the Captain noting to Bill "That's the trouble with hope... it makes one awfully frightened."
  • The Novelization reveals that the Twelfth Doctor feels this way and wants to die, in part, so he doesn't have to deal with hope anymore. Given how badly things worked out regarding his hope that Missy was redeemable (though it was still better than he believes it to be), this is understandable. But hope ends up being the last thing he feels as he lets this life go so that Thirteen can exist.
• Hope Spot: Twelve destructively regenerates into Thirteen just as Ten did into Eleven. For a moment, it seems as if the TARDIS has weathered the energy release better than it did the last time. Then Thirteen presses a button and everything goes to hell.
• I Don't Like the Sound of That Place: The Chamber of Death, where the humans kidnapped by the Testimony are kept (unconscious) to have their memories uploaded. No wonder the Doctors don't believe the Testimony could be benevolent. In truth, the name just refers to the inevitable fates of everyone there.
• I Hate Past Me: Twelve isn't thrilled by his original sexist self, to put it mildly. At one point, he tells One to stop talking. However, given One doesn't do this when Twelve isn't around (and as confirmed by the novelization), he's mostly doing it to wind him up, and it seems to be a case of the Doctor trolling and teasing himself again.
• I Have Many Names: The Testimony refers to the many sobriquets of the Doctor, such as the Imp of the Pandorica, the Shadow of the Valeyard, the Beast of Trenzalore, the Butcher of Skull Moon, the Last Tree of Garsennon, the Destroyer of Skaro, and the Doctor of War.
• I'm Cold... So Cold...: While facing death in a muddy shell-crater the Captain says, "Cold, isn't it? It's about to get colder, I suppose, for one of us."
• Impairment Shot: After the regeneration, the Doctor looks in a reflective surface to check out the new face, and it's shown from the Doctor's point of view, with a bit of blur and shake to show that the Doctor is still recovering.
• I Need a Freaking Drink: The First Doctor notes that the brandy bottle isn't as full as it used to be in Twelfth's TARDIS. After seeing his future in the Chamber of the Dead, he realizes the reason for this.
• Internal Homage: After Twelve regenerates, his ring falls from Thirteen's finger — as the First Doctor's ring no longer fitted the Second, after his regeneration.
• Internal Reveal: The Twelfth Doctor and Bill Potts each learn that the other was NOT Killed Off for Real in the previous episode; moreover Twelve learns that Bill is no longer a Cyberman. He's not entirely convinced. Turns out that this Bill is technically an avatar of the Testimony created from the memories of the original Bill, but for all intents and purposes she's the real deal.
• Ironic Echo: Bill Potts frets that she's standing right in front of the Doctor, and yet he can't seem to see her.
• It Runs in the Family: It appears The Brigadier's ancestors were just as likely to keep a Stiff Upper Lip and remember their duty no matter what fantastical events occur to them. They were also just as willing to die for their country if they had to, as well.
• The Kindnapper: The Testimony only kidnaps humans so that their memories may be downloaded and preserved, temporarily putting them to sleep so that they do not realize what has happened to them, and returning them immediately to the moment they were taken from. The only reason the Captain's situation is an exception is because the two Doctors meeting and threatening a major paradox (via One not wanting to regenerate) causes a disruption in the timeline and caused the Testimony to not able to pinpoint the exact time to return the Captain to.
• Laser-Guided Amnesia: The trope comes up twice in the denouement.
  • When the Testimony unfreezes time upon the Captain being returned to the place of his death (or so it seems), it also wipes his memory of his kidnapping and subsequent adventure with the Doctors. He does, however, seem to vaguely recognize the Twelfth Doctor during the Christmas Truce.
  • Shortly after that, the Testimony restores the Twelfth Doctor's lost memories of Clara Oswald. They were lost because he underwent this trope in "Hell Bent", originally intending Clara to lose her memories of him before Clara sabotaged the neural block and brought him to his senses — whereupon they activated it together and he got the short end of the straw since one of them had to so they wouldn't be able to keep traveling and stay together due to the Hybrid prophecy that their love fortold.
  • The Novelization clarifies that the glass avatar of Bill Potts is initially affected by this, unable to remember her many happy years with Heather because it would affect her interactions with the Doctors. After the Testimony decides the Doctor is Good All Along, Bill's avatar can remember everything.
• Late-Arrival Spoiler: Several big ones for the Series 10 finale; the first trailer alone revealed that:
  • The Twelfth Doctor doesn't regenerate, after the cold open of "World Enough and Time" suggests that it's the How We Got Here conclusion of "The Doctor Falls" — rather, he puts it off a little longer.
  • The First Doctor meeting Twelve, the centerpiece of the story and ad campaign, is the Cliffhanger of "The Doctor Falls".
  • Played with regarding the fate of Bill Potts; in the Cliffhanger of "World Enough and Time" Bill Potts is fully Cyber-converted and thus seemingly doomed to a Mercy Kill or Heroic Sacrifice, but Heather saves her and gives her a humanoid form once more in "The Doctor Falls". While the Bill seen in this episode turns out to be an avatar of the original, her form does reflect her happy fate, which she explains to the upset Doctor (who believes she died in a Heroic Sacrifice). As well, that trailer confirmed that Pearl Mackie was appearing in this episode and not as Cyber!Bill, so...
  • And of course, last but not least, not only does the Twelfth Doctor choose to regenerate after all but in a huge twist he regenerates into a woman, because the BBC made no effort to hide it. It actually prefers to publicize the new actor a little early to cash in on the buzz it generates.
• Leitmotif:
  • "The Doctor's Theme", the Doctor's original revival-era leitmotif, can be heard during Thirteen's first moments.
  • The song "Breaking the Wall", which first appeared in "Heaven Sent", and has been associated with Twelve all last season, returns when he's giving his Final Speech before regenerating.
• Let Us Never Speak of This Again: After hearing Bill call his future self an arse, One threatens her with a smacked bottom if he hears language like that again. An utterly mortified Twelve begs Bill to pretend that never happened. Bill won't agree to that, wanting it to be something they laugh about years from now.
• Lighter and Softer: As a deliberate contrast to "World Enough and Time"/"The Doctor Falls", which put the Doctor and his companions (especially Bill) through the wringer, saw Missy's Heel–Face Turn stopped in its tracks by her previous self, and climaxed with the Doctor's Heroic Sacrifice followed by his desperation to just die, this story is a much more hopeful, uplifting, funny end to the Twelfth Doctor's saga. Even the title and the crisis are more whimsical than those of previous NewWho Doctor finales. It's also the first NewWho regeneration story in which the Last Great Time War is not a major plot point (that One will eventually be "The Doctor of War" is brought up and becomes a representation of his fears for his future, but that's all, and even that moniker gets a more hopeful interpretation put on it), and one of the rare Doctor Who episodes to have No Antagonist. This follows in the footsteps of Twelve's previous Christmas episodes. "Last Christmas" and "The Husbands of River Song" were ultimately joyous codas to the extremely Bittersweet Endings of Series 8 and 9, and ""The Return of Doctor Mysterio" also looked to the future with hope even in the face of sorrow.
• Manchild:
  • When examining Twelve's TARDIS, shortly before Twelve and the Captain start talking, One gives a little hop while examining the console.
  • One calls the Sonic Screwdriver a "ridiculous buzzing toy" and has an even lower opinion of Twelve's Sonic Sunglasses. It's implied that Twelve is self-aware of this trope and that's why he doesn't want to admit that the guitar is his.
  • Twelve gives a little hop while rushing over to the TARDIS and exclaiming that "you still call it a ship!"
• Meaningful Name: "Twice Upon a Time" — as in revisiting a previous adventure with a past Doctor and both Doctors experiencing its events firsthand. Also echoes the traditional opening of a fairy tale; in the episode, the First Doctor says that much as he wishes it could be life isn't like a fairy tale, and the Twelfth Doctor says that it can be sometimes, often with the Doctor's help.
• Meet Your Early Instalment Weirdness:
  • The Twelfth Doctor meets the First (though, considering the Doctor, no instalment of his is ever non-weird). Much is made of how, at this point in his life, he still calls the TARDIS "the Ship", hasn't officially declared himself to be Earth's protector, and doesn't telegraph/state his plans to antagonists so blatantly.
  • The same goes for the TARDIS. The First Doctor's is seen in its original smaller and blocky shape as opposed to the much larger, bluer, and modernized one it now is; a few cosmetic changes like the windows, the lantern shape and the typeface of the "POLICE PUBLIC CALL BOX" placard and telephone drawer are apparent. Both the First Doctor and Bill call out the other TARDIS's windows (from their respective perspectives) as being the wrong size.
• Messiah Creep: The Doctor being affected by this trope over their many regenerations is examined. The First Doctor is shocked to realize that his later lives will come to commit themselves to defending Earth and other worlds — becoming known by such names as "The Doctor of War" in the process — rather than just stumbling into crises and finding their way out of them, partially because he believes Good Is Impotent. Glass!Bill realizes that he doesn't believe the concept of a Hope Bringer actually exists, much less that he can be that very thing. It's Twelve's rescue of the Captain from his seemingly inevitable death that makes One understand the full potential of his future lives.
• Miles to Go Before I Sleep: One and Twelve are both regenerating despite their best efforts, but end up roped into one final adventure.
• Missing Trailer Scene: The Twelfth and First Doctors' exchange "We do have one little advantage", "What advantage?", "This time there's two of us" does not appear in the episode. The scene of the Captain walking up to them and asking if either is a Doctor is also shot from different angles in the trailer, and several other shots are also missing. It would appear that the Doctors' exchange is just part of the half-hour's worth of Deleted Scenes from this episode.
• The Mole: Bill is a benign version, a Glass Avatar of the original Bill slipped onto the ship under the guise of her being the real one. Her purpose isn't to manipulate the Doctors but simply to observe them, and it's still Bill's mind so she would never harm the Doctor. (Twelve actually gathers and states evidence that she isn't the original Bill almost immediately, but this is quickly put on the back burner and he doesn't learn what her actual purpose is until later.)
• Motifs: One last set for Series 10:
  • The value of individual lives: The Doctors are facing an entity that kidnaps specifically chosen humans out of time, one by one. Why do they do it, and why are they picking these people in particular? Is it really worth rewriting history to save just one soldier from the grave? And how can each Doctor — but especially the Twelfth — be convinced to go on living (enduring Loss of Identity in the process) and helping others instead of embracing eternal rest after all their good works?
  • Exploitation: Low-key version: The Testimony is benevolent, but it is kidnapping people to access/duplicate their memories.
  • Hidden threats: Turns out that there was another crisis taking place alongside the Cybermen's first-ever encounter with the Doctor. Subverted with the issue of Glass!Bill turning out to be The Mole, as she is not a threat.
  • Imprisonment/release: Those picked out by the Testimony to be "uploaded" are temporarily imprisoned by it.
  • "Villains" that aren't actually evil: The Testimony and its Glass People are a human version of the Matrix and a benevolent version of the Nethersphere, collecting the memories of deceased humans for posterity and prosperity.
• Mythology Gag:
  • The First Doctor assumes that his regeneration will make him younger. Not only was Patrick Troughton younger than Hartnell, the original intention of the "renewal" (as it was called in 1966) was that the Second Doctor actually was a younger version of the First Doctor.
  • At the age of 59, Capaldi spent the entirety of the tenth season and this Christmas special being the oldest actor to headline the series, overtaking Hartnell in February 2017.^note There have been older actors to have played the Doctor — most notably, Sir John Hurt at 73 and David Bradley at 75 — but Capaldi is the oldest series lead.
  • The Captain's mention of Cromer is a reference to the Brigadier's mention of Cromer in "The Three Doctors" (and a hint to the kind of fan who remembers things like that that the two characters are connected).
• No Antagonist: The Glass People do plan something, but they aren't malevolent.
  Twelfth Doctor: It's not an Evil Plan. Well, I don't really know what to do when there isn't an Evil Plan.
• Noodle Incident: We know the Doctor was at Skull Moon during the Time War, as revealed in Heaven Sent, but just what the hell did he do there to be known as "The Butcher of Skull Moon"?
• Not Even Bothering with the Accent: The actor playing Ben doesn't even bother with a Cockney accent.
• Nothing Is the Same Anymore: The two Doctors don't want to regenerate because the nature of regeneration invokes this trope. They won't have the same personality and have to, in a sense, start their lives afresh — especially Twelve, who has just lost his companions and Missy, leaving him with no one who could help ease the transition as his side of the story begins. Ultimately, not only do both of them accept this trope but the entire franchise won't be quite the same because Twelve's regeneration involves a Gender Bender, resulting in the Doctor's first female incarnation. This also calls back to the First Doctor’s regeneration, which was also a major change to the franchise.
• Novelization: By Paul Cornell, which goes into much greater detail on the ultimate fates of Bill and Nardole among other things.
• No, You: Rusty's response when the Doctor calls him "a good Dalek."
  Rusty: I am not a good Dalek. You are a good Dalek.
• The Nth Doctor:
  • Obviously, since it's a regeneration episode; three Doctors appear in full, and we get glimpses of the others when the Glass People show One their archives, and when One regenerates.
  • In addition, the difference in appearance between William Hartnell and David Bradley is explained by One's regeneration already having started.
• Obligatory Joke:
  The Captain: So sorry. I don't suppose either of you is a doctor?
  [One and Twelve give each other an Aside Glance]
  Twelfth Doctor: You trying to be funny?
• Oblivious to His Own Description: The First Doctor admits that one reason he left Gallifrey was to try and answer why good always prevailed over evil when, objectively, evil should typically win because Being Good Sucks. Bill suggests that it could be because of a single bloke running around, helping where he can and maintaining good in the universe as a result. The Doctor dismisses this as a fairy tale.
• Of Course I'm Not a Virgin: The First Doctor and the Captain both feel it necessary to mention that they have "some experience of the fairer sex"; Bill promptly retorts that she does, too, much to their surprise.
• Oh, Crap!:
  • Twelve has this reaction when he realizes that he just confused an officer from the Great War by referring to it as "World War One".
  • For that matter, the officer himself is visibly stunned that all the horror and bloodshed he's seen and endured is merely the first go-round of it.
  • At the end, Thirteen's reaction to getting tossed out of the TARDIS and into freefall is the page image for Doctor Who's subpage.
• Once More, with Clarity: We see how the Twelfth Doctor was involved in "The Tenth Planet", and we also get more information about the First Doctor's condition near his demise.
• Ontological Mystery: How and why exactly is a World War One captain in the middle of the South Pole in 1986?
• Outside-Context Problem: Several times over:
  • The First Doctor was trying to avoid regenerating after "The Tenth Planet" when he ran into a future self on the way back to his TARDIS.
  • The Twelfth Doctor was also trying not to regenerate when the TARDIS elected to bring him to the South Pole and meet himself to convince him to regenerate.
  • Then the two Doctors find themselves having to deal with the Testimony.
  • To the Testimony the Doctors' presence is an outside context problem, because they accidentally caused the Captain to be returned to the wrong place and time.
  • And the Captain is in the middle of a life-and-death standoff on a battlefield of World War I when he's taken away by the Testimony in the first place.
• Plot Parallel: Both the Captain and the German soldier don't want to kill the other, but since Poor Communication Kills is in play neither realizes that. Poor Communication Kills is also the problem the Doctors and the Testimony have: the Doctors don't realize the Testimony doesn't have an Evil Plan because it doesn't just explain itself, and the Testimony doesn't know the Doctor personally and doesn't know that his actions over the space-time continuum — those that have given him the "Doctor of War" reputation — are far more often than not motivated by good intentions, even if they often ended in tragedy and destruction.
• Politically Incorrect Hero: Played with because it involves two incarnations of one character — the First Doctor is sexist compared to the Twelfth.
• Poor Communication Kills:
  • The whole episode could have been resolved in 10 minutes tops had the Glass People explained what they were doing right up front and why.
  • Also literally the case between the Captain and the German soldier (before the Doctor fixes the situation). Each of them urges the other to simply go, not wanting to kill them, but doesn't understand what the other is saying due to not speaking the same language.
• Previously on…:
  • Exaggerated, with perhaps the biggest gap in history between the "previously on" and the episode it's referencing.
    Previously, on Doctor Who
    709 episodes ago
  • It also has a twist in that rather than recapping "The Doctor Falls", it shows what the First Doctor, Ben and Polly are up to in "The Tenth Planet", the previous adventure from their perspective. From there, One leaves his companions behind and ends up walking right into the Cliffhanger of "The Doctor Falls".
• The Promise: Bill asks the Twelfth Doctor to "Come back alive" from what turns out to be a consultation with Rusty. He tells her "Be here [at the TARDIS] when I do", thus making this. It becomes a moot point.
• Retcon: When "The Tenth Planet" aired, the term "regeneration" hadn't been coined and the writers were quietly and vaguely trying to describe what happened to make the Doctor change appearance as though he just got younger and was still the same, looking for an excuse to write Hartnell out and pussyfoot away from the issue. Now that regeneration has solidified as a core concept in Doctor Who, the issue is approached more directly with the First Doctor and Twelfth Doctor openly discussing that they don't want to "regenerate" as opposed to merely "change", and the last moments of the First Doctor are treated with more eloquence and grandeur by showing he had one last thing to do before his time was up and refused to go quietly. There's also the fact that the First Doctor is shown with his hands glowing with the golden glow of regeneration energy, which is how regeneration has consistently been depicted in the revival; in the original series each regeneration was a case of Depending on the Artist, with One's simply being a fade to white achieved by exploiting a mechanical fault with one of the cameras.
• Revealing Hug: Bill Potts hugging the First Doctor, before revealing that she's a Glass Woman. Not only her expression but her glass hands are shown.
• Riddle for the Ages: While Paul Cornell's novelization (see All There in the Manual above) reveals the Surprisingly Happy Endings of Bill Potts, Nardole, and the solar farmers from the previous episode, several unanswered questions remain.
  • Do the original Bill Potts and Nardole ever learn that the Twelfth Doctor survived "The Doctor Falls"? The novelization suggests they don't, but it's not confirmed.
  • The very first glimpse audiences had of the Twelfth Doctor was of him helping his previous selves rescue Gallifrey in "The Day of the Doctor". With this episode, the question of when that happened from his perspective may never be answered.
  • And now that Bill and the Doctor's relationship is apparently over for good: Where did the spaceship that left the puddle that possessed Heather and led to Bill becoming the Doctor's companion come from?
• Running Gag:
  • The First Doctor's sexism, and the Twelfth Doctor and Bill being offended and embarrassed by it.
  • The Doctor telling his next incarnation to never eat pears was originally taken from the novel that the Tenth Doctor story "Human Nature"/"The Family of Blood" was based on. David Tennant improvised a reference to it during filming which was released online and included with the Deleted Scenes on the DVD, but not in the episode itself. Peter Capaldi's last advice to Clara before losing his memories of her included an admonition to never eat pears, "That one's important, you should write it down!" Now, the Doctor feels warning his next self not to eat pears is on the same level of importance as being kind or never telling their name. For bonus points, Paul Cornell, who wrote Human Nature and its television adaptation, wrote this episode's novelization!
  • It also gets in on the series-long running joke where almost no incarnation of the Doctor can ever enter another's TARDIS control room without talking smack about it.
    One: My TARDIS! Look at my TARDIS!
    The Captain: It's impossible...
    One: Have I been burgled?
    The Captain: But it's-
    One: Hideous!
• Saying Too Much: The Captain is naturally disturbed to hear the Twelfth Doctor refer to the Great War as World War One. It's a good job the Doctor didn't say he'd taken part in World War Six.
• Seen It All: When Bill discovers the Doctor has brought her to a devastated planet where someone really wants to kill him, she just sighs and follows him out.
• Self-Deprecation: Twelve says he'd tell One to "stop being an idiot, but [he] knows what's coming" — reaffirming the way he described himself in "Death in Heaven" — and downplays Doctors Two to Eleven as "a few false starts" when the First Doctor asks if Twelve is the man One will become.
• Series Continuity Error: The Previously on… segment claims that the events of "The Tenth Planet" happened "709 episodes ago". Discounting the fact that this is only how far back the first episode of that story happened, this numbering excludes "Shada", which is odd considering that story was completed with animation the same year this episode was released. All things considered, "The Tenth Planet" could more accurately be said to have happened 712-715 episodes ago.
• Silicon-Based Life: Glass People are humanoid but completely see-through when they aren't serving as avatars of the dearly departed, like living glass sculptures.
• Stable Time Loop: The Twelfth Doctor can't exist and be brought back to the past to meet his original self unless the First Doctor regenerates, and at the time Twelve arrives One doesn't want to, so the story involves Twelve creating this — which ends up helping him accept the prospect of his own regeneration along the way. The possibility of the loop not being created and the disastrous paradox that would take place if both Doctors died at once causes the temporal disturbance that interrupts the Testimony returning the Captain to the battlefield in the first place.
• Straw Misogynist: The First Doctor comes out with a string of Stay in the Kitchen remarks. These appear to set up the Twelfth to tell him he's wrong, and to be the butt of I Hate Past Me jokes.
• Sunglasses at Night: One mocks Twelve for wearing sunglasses indoors, regardless of how functional they are. Twelve gets One to try them, but changes his mind when One sees something labeled "Browser History".
• Take Me Instead: The Captain, upon seeing how much Twelve cares about Bill Potts, offers his life to the Testimony in exchange for hers. This is before he and the Doctors understand exactly how it works and what its purpose is, and moreover that Bill is an avatar of it.
• Technobabble: When the Glass Woman explains to the Captain that he won't remember what happened and a perception filter will hide their presence once time resumes, he says that he assumes the words they just spoke probably meant something.
• Tempting Fate:
  • Twelve asks Bill to respect him "as I have always respected you." Bill promptly calls him an arse, then his younger incarnation appears and threatens to give her a smacked bottom.
  • "Probably just rats. I'm used to rats." Cue the Face Hugger.
• This Is Reality: When the First Doctor tells Bill that he's trying to understand how good prevails in an unkind universe, she suggests that it might be because there's somebody who goes around fixing things when they go wrong. He says that it's a nice idea, but he doesn't believe it because real life isn't like fairy tales.
• This Is Something He's Got to Do Himself: The Twelfth Doctor leaves Glass Bill behind at the TARDIS as he heads off to consult Rusty, leading to The Promise above. He also regards his regeneration as this, leaving Glass Nardole and Glass Bill behind to return to the TARDIS alone at the end.
• Time Crash: There is a critical paradox at the heart of this episode. If the First Doctor doesn't regenerate, then none of his future incarnations will exist. If he does it in the same time and place as one of those future incarnations, that's even worse.
• Time Stands Still: The battleground freezes, both literally and... well... literally, at the appearance of the Doctors. This is the work of the Testimony, who travel through time and freeze moments to kidnap humans.
• To Make a Long Story Short: How come Bill is Not Quite Dead after being turned into a Cyberman? "Well, long story short. I totally pulled."
• Tomato in the Mirror: Averted. In the episode Glass!Bill seems to know from the start that she's not the original (and in fact, not even human). She isn't particularly bothered by the fact and otherwise acts completely normal. The novelization gives this more depth: she is confused as to why she can't clearly remember her entire life with Heather. This is because the Testimony gave her Laser-Guided Amnesia so she'd interact with the Doctor as she did before they were parted, to better serve as The Mole. Once the Testimony is sure he is trustworthy and benevolent, all of her memories are restored.
• Took a Level in Jerkass: While he was never entirely free of chauvinism, the First Doctor is made a lot more overtly sexist than he ever was in his original adventures and "The Five Doctors".
• Too Much Information: Nardole's glass nipples.
• Trash the Set: Just as with what happened with his tenth incarnation, the Twelfth Doctor's been holding back his regeneration for so long that when he finally lets it happen, it wreaks utter havoc on his TARDIS. After the regeneration, everything seems to be quiet, but when Thirteen pushes a button on the console, the TARDIS starts exploding again.
• Walking Spoiler:
  • The Captain. Nothing was revealed in promotional materials about him but his rank and temporal placement (World War I) even as Mark Gatiss was billed before Pearl Mackie in the trailer, Capaldi said he has a key role in the Doctor's lives, and he's the specific prey of the Glass People. Turns out he's one of the Brigadier's paternal ancestors. (Incidentally, the novelization gets around the issue of his name in the scenes told from his viewpoint by just calling him "Archie".)
  • For that matter, the Glass People/The Testimony themselves: The spoiler is they aren't actually villains, meaning the Doctor doesn't have an evil plan to thwart for once.
• War Is Hell: Lampshaded by the Captain as he's in a standoff with a German soldier that he really doesn't want to kill, but knows he will anyway to prevent himself from being killed.
• The Watson: Along with previously-established companion Bill (albeit as a glass avatar), the Captain is this. In early drafts Bill wasn't even included precisely because she'd already had her Happy Ending in the previous episode and the Captain filled the function of a character the Doctors could explain things to, but Moffat decided the story needed more "fun" and found an unusual way to bring her back (and lift unwarranted guilt from the Doctor regarding her fate, which he felt at least partially responsible for and was not able to remedy). He mentions at times that he is "lagging behind" on what's going on.
• Wham Episode: The First and Twelfth Doctors meet near/at the end of their respective incarnations, and the Twelfth Doctor regenerates into their first female incarnation. Otherwise, no major changes are made to the mythos.
• Wham Line: Near the end of the episode, we finally learn the Captain's full name: Archibald Hamish Lethbridge-Stewart.
• Wham Shot: The first trailer has no less than three of these.
  • Polly sees the First Doctor's hands glow with regeneration energy, in the same way that regeneration has been shown in the revival.
  • Bill returns! (As it turned out, sorta!)
  • Although it's really just another Testimony avatar, similar to the last time the Doctor regenerated we do get one final appearance from Clara and this definitively removes the Doctor's memory block from "Hell Bent", allowing him to regain his memories of her.
  • And in the actual episode, no sooner has Thirteen finished her regeneration than the TARDIS tips sideways with its doors open and she's flung out in midair high above the Earth.
• What Happened to the Mouse?: Nardole and Bill Potts's lives post-Doctor, up to and including the nature of their deaths, remain mysteries in the episode, though the novelization reveals them each to get a Surprisingly Happy Ending (see All There in the Manual above). In the meantime, the faculty and students at St. Luke's have to be wondering what happened to that particularly long-tenured professor who just disappeared one day. For that matter, what becomes of the now-empty Vault?
• What Measure Is a Non-Human?: Downplayed — the Twelfth Doctor quickly figures out that Bill isn't the real Bill, and thus holds her at arm's length emotionally, trying to poke holes in her behavior and speech. Because Glass!Bill is created from the original Bill's memories, she has the same personality, way of thinking, and emotions, and is deeply hurt by his standoffish attitude, pleading with him to regard her as no different than the real deal. Although he does come to understand why the avatars exist and that they are good, and comes to treat them with kindness and appreciate the comfort (and memories) they give him, he never quite manages to just treat them as he would their human (or cyborg in Nardole's case) counterparts. After all, the existence of the avatars confirms to him that the originals — dear friends of his — are dead and gone, and that knowledge does not bring him much comfort at a very trying time of his life. The Novelization also explains that the Doctor is still wracked with guilt over his failure to rescue Bill from being Cyber-converted back in "World Enough and Time", which is one reason why he's so upset with the Testimony sending out an "imposter" who has her original form.
  • The novelisation confirms that Nardole's being saved from death in the Testimony is an exception, and that its designers intended it to only save humans.
• Who Wants to Live Forever?:
  • At first. The Twelfth Doctor is really feeling his age, likening his lifespan to a deserted battlefield with himself as the last man standing. But then again, by the end of the episode this is subverted, as the Doctor is convinced that there are things Worth Living For and regenerates.
  • The Novelization reveals that Bill Potts came to feel this way. As much as she loved living the life of an immortal Pilot with Heather, their subsequent life as humans on Earth was even happier, and she ultimately chose to die as a human when that body became old and infirm rather than return to immortality. For her part, Heather did not feel the same way, and Bill's dying request was for her to return to the stars and live as she wanted to. While Bill's avatar does understand the Twelfth Doctor's concerns in the end, she does not think he can afford the "luxury of mortality" because there's still so much good he can do for others if he regenerates.
• Winter Warfare: The Captain comes from a World War I front line that's covered in snow, at a moment frozen in time to boot thanks to the Testimony, who have to follow him to the snowy South Pole and freeze time there too.
• Women Drivers: Averted. Though the TARDIS does explode and throw Thirteen out into freefall as soon as she tries operating it, this isn't because she's a woman. This is because the Doctor has failed to learn from past mistakes and regenerated inside the TARDIS again despite the previous three times they did so causing problems. The Novelization suggests that the regeneration is not the reason the TARDIS goes haywire, because it's starting to malfunction before he regenerates. Twelve even notices this, but it's too late for him to do anything about it...
• Worth Living For: The Twelfth Doctor has just been put through the wringer, is dying, and has no companions to comfort him. He believes his attempt to induce a full Heel–Face Turn in Missy failed and that Bill was Killed Off for Real after being Cyber-converted by Missy's previous self as that villain's cruel response to the Doctor's efforts. If he regenerates, he'll lose the personality and appearance he's grown to be happy with and have to adjust to a new one all over again, and owing to his perpetual Chronic Hero Syndrome he'll face more dangers, more successes but also failures, and more friendships with mere mortals that will inevitably end in loss; in this life alone he lost two women he loved with all his hearts (the Novelization makes this especially clear with regards to River Song). Couple that with once again being essentially exiled from his homeworld on top of all this — just because he tried to defy the Web of Time and save someone he loved from the grave, which wouldn't have happened if his people hadn't been plotting against him — and he's determined to die for good. In the end, however, he decides to keep going after he realizes that being able to help others is Worth Living For.
• You Wouldn't Shoot Me: The Twelfth Doctor convinces Rusty the Dalek not to kill him because he would rather see him die.

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"Doctor... I let you go."

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"Oh, brilliant!"
BOOM!

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