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    "The Pilot" 
  • Why doesn't Bill recognize the Daleks? Because the episode confirms that she's from The Present Day as was announced, and so she would have lived through a Dalek invasion several years before. And yet it's clear she's never seen them before.
    • The majority of attacks on the civilian population in "The Stolen Earth" seem to have been carried out by Dalek ships, not Dalek ground forces. Their actual troops seem to have been targeting military outposts, Torchwood, UNIT, and known associates of the Doctor. It's likely that most civilians - at least, the ones who didn't get EX-TER-MIN-ATE-ed in the encounter - never saw what the invaders looked like or learned what they were called.
    • Also bear in mind that Amy had no idea what a Dalek was, either, and it's heavily implied that the cracks in the skin of the universe are responsible for causing a large portion of the population to forget events like this.
    • Yes, the cracks did erase things, but it's strongly implied that after the Doctor rebooted the universe at the end of Series 5 that everything they ate was restored. Also, although the above point about attacks on civilians mostly being carried out by Dalek ships is a good one, remember that Amy was a civilian too, and the Doctor was incredibly disturbed by her non-recognition of the Daleks, suggesting that at least images or descriptions of the Daleks themselves were/are well known to the population of Earth after "The Stolen Earth"/"Journey's End" even if they don't know what they're called — which they probably should be, given that the Earth was forced to formally surrender, and the Daleks repeatedly identified themselves while rounding up humans.
  • When the Doctor tries to shake off pursuit by traveling to a planet at the other end of the universe, why did he go into the future rather than the past? Wouldn't traveling to the past be a better option? The oil-slick entity seems to be able to sense where Bill is heading, but up to that point it wasn't clear that it could Time Travel. Hopping into the future would give it millions of years in which to get to where Bill was going to appear, even if it had to take the long way around; going a similar distance into the past would deny it that option.
    • Maybe the Doctor could sense that the creature had only just arrived in the future rather than coming the long way around? And to be fair, he does go to the past immediately after (the Dalek/Movellan battle is stated to be in the past,) just not to test the thing's time-travel capabilities.

  • Given that A.I. Is a Crapshoot is a trope prominent to science fiction, as well as something that has shown up more than a few times in Doctor Who, you'd think that somewhere along the way, someone would have figured out how to make robots Three Laws-Compliant, or at the very least, program in a specific set of variables for caretaking robots, rather than vague directives like, "Keep humanity happy". You know, something more along the lines of "Ensure that pulse and heart rate are within these limits. Oxygen levels should be about here. By the way, don't kill people." So why do we still have robotic life forms running around killing folks, even if it wasn't done in malice, but out of Blue-and-Orange Morality?
    • For all we know, they were Three Laws-Compliant, but their definition of "harm" (as in "do not harm a human being") was flawed. If they honestly had cause to believe that grief was a fatal disease - for instance, if someone in mourning for the old woman actually killed themselves or suffered a fatal accident due to grief-incited carelessness - they may have fallen afoul of the Zeroth Law and concluded that stopping the "contagion" was necessary to protect the sleepers from whatever was "infecting" the gardeners.

    "Thin Ice" 
  • Did the Doctor seriously let Spider die? Or did he simply wait to jump for the screwdriver at the last moment because he didn't want to break the ice and fall in himself?
    • At that point he wasn't entirely sure what was happening, and didn't have any idea that the creature could break and re-freeze the ice to pull people under. As far as he knew, the best approach was to try and convince the somewhat small child to slowly come back off the thin ice, rather than go barreling out there, add more weight to it, and likely cause Spider to start running. Once it became clear he was going under, the Doctor tried to grab him, but it was too late. The conflict with Bill in the next scene wasn't really about the Doctor letting him die, but rather the Doctor not seeming to care about it after the fact.
  • How did the Doctor and Bill know that Sutcliffe didn't already have a legitimate child as heir, whom they'd be unjustly disinheriting with their little forgery-ploy? Nobody ever mentioned his marital status in the episode. Granted, he wasn't wearing a wedding ring in his scenes, but that doesn't mean he couldn't be a widower who'd moved on.
    • The Doctor is shown altering Sutcliffe's will. Presumably, if he'd had any legitimate heirs, the will would've mentioned them.
  • When the Doctor and Bill are underwater in their old-timey diving suits, where do they get the air to breathe? No one is pumping air into them from above the water, which is how they work.
    • The Doctor could have modified either them or the pump.
  • Bill says that the death of Spider is the first time she's seen anyone die. When the Doctor mentions the dead space colonists from the previous episode, Bill says that that's different, because they were already dead when the two arrived on the planet. But at the end of "Smile" the Vardies do consume one of the colonists who woke up from hibernation while Bill is there to see it.
    • The Vardies work very fast. It's likely that the colonist was consumed so quickly that Bill didn't really register it.
    • She was looking at the Doctor, not the defending colonists, when it happened. Probably she didn't even notice the guy had vanished until later.

    "Knock Knock" 
  • Why did the evil landlord always feed the dryads exactly 6 students, and exactly 20 years apart? Nothing in the episode indicates the dryads couldn't just eat anybody at any time. And you'd think the disappearance of six students, most of whom probably had given the address of their new home to their parents etc, would have drawn the attention of the cops to the house and its owner? Especially since he kept the belongings of the missing students in the basement? Wouldn't it have been easier and less suspicious if he'd just fed the dryads with someone few people would miss, like a homeless person, every three years?
    • Well, you know, he doesn't want anyone to know what he's doing, and if he does it more often he might get attention. As for why students specifically, it's mentioned that younger people have more energy, more lifeforce for the dryads to consume. University students are probably the youngest he can go without attracting unwanted attention, as people who've just left home and asserted their independence.
    • Again, if he didn't want attention, six students disappearing on the same day from the same address would certainly bring him that. He could've easily gone to another part of the city, find some young homeless people, tell them he's running a place for the homeless to live, and bring them to the house. That way it would be much less likely for anyone to connect the disappearance to him and his house. And it still remains a headscratcher why the cops never searched the house and never found the belongings of the disappeared students, since they weren't exactly well hidden.
    • The house started eating the students the same day he showed them the place, and would have finished them all off by morning if not for the Doctor's intervention. With no cell reception or wifi today, and no landline phone or evening mail service in previous decades, it's unlikely that any of the students had the chance to inform their families that they were moving to that address.
    • They didn't move the same day. Only Pavel is shown to move there right away, the others went to their homes to pack their belongings... Which would give them plenty of time to let their families and loved ones know where they're moving.
    • One could say that the insects ate the cops/inspectors/etc. but that would draw more attention. The Lanlord says he "kept their lives a secret" so he must be doing something when he's not luring kids to the place.
    • As for why six students, that's how many bedrooms the house has, not counting the secret one in the tower. (They did say there wasn't a spare bed available for the Doctor.) So naturally it'd be groups of six that would be most interested in renting the place.
    • A deleted scene shows the landlord explaining that, twenty years after the dryads cured Eliza, they went dormant and Eliza started getting sick again. Then a vagrant broke into the house, and fell asleep. The dryads ate him, and Eliza got better. Presumably it was through trial and error that he settled on six people per feeding cycle.
  • Why did the Dryads turn the landlord's mother into some kind of immortal wood-nymph? What exactly do they gain from doing this?
    • We don't know why the dryads started doing it, but they kept up with it because the Landlord trained them to do so.
  • Why is the Doctor not the slightest bit concerned that a huge horde of ravenous insects, ones that are capable of destroying a large house in moments and clearly don't shy away from eating people, is now loose in the heart of a major population centre?
    • Perhaps Eliza did a Taking You with Me. Another possibility is that the insects were only dangerous because the Landlord directed them to be so. After all, he found them in a garden and found out by accident what they could do. They weren't causing trouble back then so they could be naturally benign.
    • A deleted/alternate ending scene shows the students in a newer-looking but still mostly wooden house, with open windowshades and a party atmosphere, and Bill remarks that the house feels friendlier. The Doctor explains that Eliza won and took control of the dryads, giving the house an entirely new personality. He also speculates on whether perhaps the dryads are native, and exist in every house....
  • The students complain to the landlord that the house has old-fashioned sockets, so they can't get electricity for their modern appliances. How did Pavel get his turntables to work, then? They look pretty new.
    • Batteries?
    • Unless I'm missing some other significance to the set-up, he seems to have jury-rigged them to the light.

    "The Pyramid at the End of the World" 
  • So, World War III is looming, with the U.S., Russia, and China all about to confront each other, as this episode begins. Given that the Doctor's been on The Slow Path lately, shouldn't he, Nardole, and Bill have been at least a little concerned about this in previous Series 10 episodes? An impending world war should be the top of the news worldwide — and though the Doctor's President of Earth duties apply specifically to turning back alien threats, he should be aware of more mundane crises of this scope and scale, if only because Missy's down in the Vault. But not even Nardole's brought up this kind of situation as a reason for him to stick to present day Earth. The Doctor might, being the Doctor, already know that this crisis will turn out okay (at least before the pyramid and the Monks turn up), but Bill and her friends and family wouldn't. They've never discussed it even in passing; she's been busy with school, dating and finding her own place when she hasn't been traveling with the Doctor. Even in the simulation created by the Monks, there was no one expressing concern over potential war; even with the Veritas starting to be spread, wouldn't that mentioned in passing at the Pentagon or Vatican (especially the former)?
    • The situation with the armies is neither as dire nor as tense as the previews implied. Although the armies are surrounding a disputed area in Central Asia, they aren't actually about to start shooting at each other if someone sneezes. World War III isn't actually about to start, that's just misdirection by the Monks to distract the Doctor, the UN and the superpowers from the true threat — an accidental release of killer bacteria.
  • Who the hell designs an airlock that can be left open at both ends? That defeats the entire purpose of an airlock! Furthermore, whoever designed an air purification system that not only vents out potentially ecology-destroying chemicals into the atmosphere, but does it on an unstoppable timer with no form of manual override, is an idiot (I am aware that the venting system likely only applies to the area outside the airlock, but it's still stupid when taken in conjunction with the airlock issues). Additionally, what kind of hack biochemical research lab can't afford a braille combination lock? Given that provenance of disability discrimination laws, one would find it criminally negligent not to be able to accommodate for people with visual impairments.
    • A lot of issues with the lab's safety could have been resolved with some clearer dialogue. The place makes GM fertiliser, and it looks more like the suits and doors are meant to protect the crops from outside contamination rather than the other way around. In these facilities the "airlock" is used as a changing and decontamination facility to make sure the lab stays clean. This is also why the venting system is set up like it is. As far as the lab is concerned there is nothing harmful to the outside in it. Erica could have said as much in protest to the Doctor - "We just make fertiliser here, not bioweapons! These suits are to protect the plants more than us!" etc etc. Also Erica's reaction to Douglas' figures implies she knew that something like this could happen, in which case the lab should have been a lot more secure and with way more oversight.
    • Additionally, a quick look at the Real Life section of Disaster Dominoes shows just how something like this can happen all the time due to poor planning and lack of oversight. The designers of the airlock either thought or were instructed to create something that could open in an emergency, thinking that their workers would know not to leave it open in normal circumstances. Idiotic indeed, but just the sort of mistake that is all too common in real life.
  • How did the UN know to contact Bill? She has only been with the Doctor for a short time, and her only adventure on Earth was during "Knock Knock" and was a small scale one. Since they asked for her help to contact the Doctor, it looks like he did not stay in touch with them since he has started to guard the Vault.
    • He probably made contact with UNIT and the Osgoods once his decades-long sojourn in Bristol reached that point in Earth's timeline, if only to resume keeping tabs on the Human/Zygon Treaty. Just because he's accepted a new responsibility to watch over the Vault doesn't mean he's lost sight of his previous obligations.
  • During the countdown in the lab, why didn't the Doctor tell Bill about his ability to regenerate? That way Bill wouldn't have needed to give her consent to the Monks, because she'd know the Doctor wouldn't actually die.
    • It seems pretty strongly implied that he can't regenerate after being blown to smithereens.
    • And even if he weren't blown to pieces, there's a good chance he would have been severely burned, suffered severe damage to his lungs from fire and smoke inhalation, and risked asphyxiating, especially since there was no way for Erica to get him out of the lab to safety for at least several minutes. Such injuries could easily shut his body down before the regeneration energy could do anything to fix it, ala the drowning of the Doctor in "Turn Left"'s alternate timeline.
  • With all the hate for Bill doing the rounds because of her choice to make a Deal with the Devil and consent to the Monks' takeover, let me ask this: Just what should she have done? Let the Doctor die? Because "Turn Left" shows us exactly how bad that would be. Either she lets the Monks win but with the Doctor alive and possibly able to do something about it, or she lets him die and the Monks take the Earth anyway with no one to stop them. They weren't "giving up" as some people say (because the doomsday clock went backwards), that was just another misdirection to get their real target, Bill, into the right place at the right time. Call her selfish all you want, but what other options did she have? The blame should go to the Doctor for not warning her about his blindness and informing her that he could (probably) survive being blown up thanks to regeneration.
    • There's an excellent point here. The Nerdist review outright stated the episode was all about misdirection, so why wouldn't the Monks be deceiving everyone about how they intended to get consent to conquer the planet?
    • It's also worth noting that the Doctor was blinded saving Bill's life, and it is that blindness that put him in danger of dying. It's pretty likely that one major factor in Bill's decision to accept the Monks' offer was due to guilt on her part for being the cause of the Doctor's blindness, even though it wasn't her fault — her spacesuit was malfunctioning.
      • What makes this sadder was that the Doctor may not have told her about his blindness because he didn't want to make her feel guilty or worry about him. As far as he was concerned, it was HIS fault she almost died, because he insisted she and Nardole come with him aboard Chasm Forge in the first place. And there's a bit of pride there too — hey, he's the Doctor, he's been through all sorts of problems, he doesn't need pity, he can still be awesome. Really, he meant well in not telling Bill, but didn't think about the problems it might cause down the line..
  • The Monks' definition of "consent" is pure sophistry. They say consent should be given out of love, not fear, which would imply whoever gives it should love them. But Bill gives her consent because she loves the Doctor and doesn't want him to die. If it's that easy, why didn't the Monks show the UN Secretary General images of his family dying in the upcoming disaster? Then he would've given his consent out of love for his family. And Bill also gives her consent because she's afraid of what would happen to Earth without the Doctor around, but apparently that doesn't count as fear?
    • For all we know, the Secretary-General may have been mostly afraid for himself, and his references to his family and world were a pretense to avoid looking like a selfish coward. The guy was a politician, after all; he knew how to put up a noble front. Bill was in no personal danger to speak of - at worst, she'd have had to pop into the TARDIS to escape the bacterial apocalypse - and her love for the Doctor was sincere and immediate, above and beyond her concern for the planet at present or in future.
  • We saw in "Under the Lake" that the Doctor could use the sonic glasses to transmit video. I understand he couldn't see the lock himself and that the information being fed to him by the glasses wasn't enough to determine how to move the numbers, but couldn't he have sent pictures or even set up a video chat (we know they can email) with Bill (or anyone else on the planet, for that matter) so she (/they) could be his eyes and describe to him how he needed to move the numbers on the lock? In fact, he'd tried to get Nardole to use the lab's cameras to take a visual on the lock for that exact reason (but of course Nardole was unconscious). Maybe the ability was disabled when the glasses had been modified to help him now he's blind, but there was no handwave given.
  • Alternatively, there was a ton of alternative ways that the Doctor could have escaped from the room. Why not use a smartphone to take a photo of the lock? Or use Face Time as a guide, with Bill providing help? Come to think of it, shouldn't there have been a Braille function for the manual lock?
    • Using their phones may not have been an option, if the Doomsday Clock countdown is all the devices' screens will display.
      • That's a good point about the phones. However, I believe the exact quote was "So now every clock in the world is the Doomsday Clock?" suggesting it was only the phone's clock that was impacted, not that the phone's control was being overridden. One thing I did pick up is that at one point Bill's phone beeped, she looked at it and said "It's the Doctor" and answered it. This suggested it could display other things (incoming caller names at least). None of the computer screens in the episode seemed to display anything unusual. So as far as I can tell all technology except for clocks should have still worked as normal.

    "The Lie of the Land" 
  • So, why exactly did the Monks want to conquer Earth? Based on what Missy says they seem to be a conqueror race, but they still have to have some reason for choosing which planets to conquer. We know they have superior technology and godlike powers (being able to restore the Doctor's sight in an instant, even when his Gallifreyan technology couldn't do that), so what exactly do they gain from taking over a backwards planet like Earth? This wasn't explained at all.
    • There were many possibilities. They could have wanted to make us into a slave labour force. Given there apparently only a handful of Monks involved in the invasions and billions of humans we could have been quite useful to them while still being incapable of resisting them due to brainwashing and our level of technology (advanced enough not to be completely useless, not so advanced as to threaten them). They could have wanted to strip the planet's natural resources. The Earth may have been in a convenient location for invading other worlds. All of these are just reasons invasions could have been justified, but as you say it never was explained.
    • Considering how specifically they insisted on being asked to take over, it's possible that the Monks' interest was more esoteric than practical: as a Reality Warper race, they might well require the adulation of a more materially-based species to reinforce their own cohesion as a species/culture. If you can hypothetically make anything happen, it may not be so easy to maintain an identity or agenda without outsiders to affirm your "role" in things. Which would explain why they ran like hell as soon as their brainwashing failed, and why they'd even bothered hunting down the few humans who remembered the truth: they'd wanted humanity to maintain them as "honored overlords", not turn them into "evil invaders" by collectively thinking of them that way.
  • Shouldn't the Monks be keeping an eye on the one person who's the linchpin to their whole brainwashing scheme, instead of letting her freely run to the Doctor and then attack their base?
    • In short, yes. In fairness, they may have assumed that no one knew she was the linchpin to their operation (even the Doctor didn't until Missy mentioned it and the Monks had no way of anticipating that). So from their perspective, since they couldn't kill her, it may have made more sense to let her run around and live a normal life rather than lock her up somewhere that would make her seems suspiciously important or keep her under special surveillance which would probably require human assistance given they had relatively few numbers (again risking showing off her importance).
    • According to Missy, the Monks don't know about the person who gave consent becoming a lynchpin. Usually the lynchpin leads a normal life and passes on the link for many generations, and the Monks assume they've won "through, they think, ruthlessness and efficiency." If the last lynchpin in a line dies, the thlose their hold and retreat, "they just chalk it up to experience." So if there's a Headscratcher here, it's that the Monks haven't ever realized their importance in the first place.
    • That's a good point. They obviously know how important the person is in the first place, since they evidently aren't willing to try conquering a planet without getting consent and they then do build all the statues so they must understand enough about the psychic link to know they need that point in the step. At some point they must just assume, "Sure, we needed them to take over, but that takeover's done now so we don't need that thing anymore." It does raise a question though around why a species which is apparently patient enough to simulate an entire world to figure out the best way to attack it, don't even do simple post event analysis to properly analyse why their own invasions succeed and fail or even really how their technology is working.
      • It depends on how often it happens and what the circumstances are. The Monks are blocking existential threats to the planet in question, so natural disasters are unlikely to have any effect and if they're not paying much attention, they'd lose track of the descendants of the linchpin easily. Say they conquer 80 planets and they lose three. One's because Missy's apparently gone around just murdering people left and right. They'd assume that it was related to the number of deaths. Let's say another planet had the descendant of the linchpin die in an accident. The monks might assume that the species just kind of shook off their control and decided to leave that planet alone in the future. Especially since, even with monk control, a lot of people will be dying all the time, just via stuff like old age and random minor accidents. If they lose very few planets and don't understand part of their central mechanism for control, they're very easily gonna rationalize it as their control just sometimes fails in the long run for no apparent reason, it sucks for them, but it happens.
  • We see the Monks killing some dissidents with their lightning, so not all of them were merely sent to prison. So when the Monks erased the memory of their conquest, what do people now think happened to those who died? And at the end of the episode, why doesn't Bill seem to feel at all guilty for allowing the Monks to take over and cause all these deaths?
    • For the first part, they'll presumably be assumed to be missing and eventually be accepted as dead. For the second, that's a debate that's being doing the rounds about whether her actions were justified or not. That's not one I'm going to get into here (out of caution for starting the same debate again), other than say if she does, we wouldn't necessarily know.
    • Speaking of guilt over needless deaths — doesn't the Doctor feel guilty, given he was broadcasting the propaganda that encouraged all those people to be captured in the first place? He was working on his plan all that time and needed the Monks to trust him, and it was for the greater good...but that doesn't gibe with him refusing to kill Bill later on as the easiest way of stopping the Monks. Does he truly value every life, a major theme of this season especially, or just those he knows personally?
    • The Doctor does value lives he doesn't know personally. We've seen him save the lives of countless strangers at the risk of his own. He does however morally object to the argument of "sacrifice one life to save a dozen, it's a bargain". That's a traditional argument in warfare (and one I can personally see the reason for) but not one the Doctor can agree to. He wasn't going to take the easier way of stopping the Monks for that reason but if it'd been his life he had to sacrifice he would have, and in fact that was exactly what he tried to do in the previous episode (telling Bill to not make the deal, therefore accepting death for himself, both in the way regeneration is death for the current Doctor and since regeneration was by no means guaranteed, at the benefit of stopping them). Of course, he'd feel guilty about the people he couldn't save but whether he was up there broadcasting the propaganda or not they'd still have died. The Giant/Head Monk and its transmitter were doing the bulk of the work, after all. At least by cooperating he was able to survive long enough to stop them eventually (from an out-of-universe perspective, I don't see why the writers made it take six months before the Doctor fought back compared to his track record, but in-universe he apparently didn't see an opportunity).
    • If not making the broadcasts could've changed anything, Twelve might indeed feel guilty about playing the role of their propaganda-source ... but remember, the Monks already have a perfect simulation of the Doctor at their disposal, which they could just as easily reprogram to fulfill that role if the real Twelve refused. Had the genuine article opted not to play the part, the same broadcasts would've taken place; they'd just be coming out of the Monks' sim-Earth, not the actual prison ship. So the real Twelve might as well play the part for whatever advantage it gives him in deceiving and undermining the Monks.
  • How exactly does the forgetting of six months work? Are people aware the time passed but just no longer aware of what happened during the time (the whole world having a mental block so no one thinks or asks about it)? Or do they all genuinely think it's six months earlier (and don't know why it's summer in winter/winter in summer)?
    • There's probably some "same-old, same old" thing in place. They can't remember anything in particular but there's no blank space.
    • They'd remember all the routine aspects of life that haven't changed during those six months - working, going to school, watching TV, whatever - while forgetting that they'd passed dozens of giant Monk-statues or seen Twelve spouting propaganda on the telly while doing so.
  • Did the Doctor's "regeneration" actually use regeneration energy, or was it some sort of illusion? It would've been quite a waste just to play a ten second trick on Bill.
    • I suspect it was just an illusion. If TV can fake a regeneration, the Doctor should have the technology.
      • For that matter, if the Doctor can fake his own ghost last season, he can certain fake his own regeneration-energy.
    • Furthermore, why make it look like he was regenerating at all? As has been discussed at length, if the Doctor had told Bill about regeneration last episode, she might not have made a Deal with the Devil to spare his life. The fact that she doesn't know he can regenerate is actually a crucial plot point. So why go to the effort of creating an illusion of a process she has no knowledge of?!
      • There seems to be a fair bit of information around about the Doctor for people who want to look. It's possible she could have learnt about regeneration at some point without the Doctor knowing. So he might have thought it was safer to fake a regeneration in case she knew about it rather than to fake dying without regenerating which would convince her he was an imposter if she did know about it.
      • "The Doctor Falls" suggests otherwise. Bill doesn't know the significance of the golden glow when they're talking in the woods, and it's clear that she doesn't think he can recover from destroying Floor 507. She and Heather simply leave his body in the TARDIS, not sticking around to see if he gets better. If she knew about regeneration's nuts and bolts, this ending would have been a lot different.
    • He may have thrown that part in just to mess with Nardole's expectations, to make his aide wonder if somebody'd forgotten to swap out the blanks.
  • Why did the Monks blindly trust that the Doctor would happily serve them and have no ulterior motive after he spent the previous episode fighting them tooth and nail? The Doctor does have Plot Armor so Bond Villain Stupidity came into play here, but they were depicted as being able to sense insincerity in the previous episode, and despite their small number one of them could easily have an eye on him at all times. Instead, they do absolutely nothing to stop him, suggesting they didn't pay attention at all provided the broadcasts were coming in. Did they even try brainwashing him?
    • It seems the Monks thought they'd brainwashed everyone on Earth, the Doctor included. Some people were resistant but the Monks could only tell when they acted out of the ordinary and started talking about how the Monks didn't belong. If the Doctor was playing along, the Monks had no way of knowing he wasn't brainwashed. As long as he proved useful to them and promoted propaganda, they had no reason to kill him.
    • It is also implied that they can only sense sincerity during their "Is your consent pure?" thing which they already did with Bill. Rule #1: The Doctor lies. It just so happens that he lied to them with the truth; as discussed at the end, the History Repeats aspect of humanity never learning from mistakes and getting themselves in trouble really does annoy him.
  • Bill's decision to shoot the Doctor makes her look stupid at best and downright insane at worst. She knows the Monks can and have brainwashed people, yet she takes the Doctor's Motive Rant as absolute proof of his deliberate and conscious betrayal made of his own free will rather than seeing him as a another victim of the Monks who needs to be saved, which is surely what he's pretending to be. Why did she jump straight to the conclusion of "You're an evil traitor, die!" instead of "Oh no, they're controlling you too?"
    • Part of this might stem from her anguish at her one great hope for the world being saved instead joining the baddies, which might have distracted her from considering the reason he did so. It's been a long six months for her, and to protect herself she couldn't discuss things with anyone else lest she be arrested (hence her conversations with her imagined mum).
  • For that matter, why exactly was her being willing to kill him the proof the Doctor needed to know she wasn't brainwashed?
    • The Monks think he's useful so they aren't going to kill him in what he thinks is a Secret Test of Character towards he himself. As has been stated other places, Bill doesn't know about regeneration.
  • I might be missing something here, but why was the one kid sent to a labor camp for possessing comics?
    • They were probably made before the Monks' invasion, and not referencing them as they should. It's also possible the Monks have been changing the stories to appear there as supporting characters (so that, say, Superman has a Monk mentor), and trying to destroy any existing material that disagrees.

    "Empress of Mars" 
  • It was never explained in the episode why the Ice Queen and her soldiers had gone into hibernation? Based on what she says, when they went to sleep the Ice Warrior civilization still existed and Mars still had an atmosphere, so why did they do it?
    • At least a few of her remarks to Friday seem to hint that she'd been on the losing side of some intra-species conflict, and had herself and her troops buried in hibernation in hope of out-living the opposition.
  • When Bill first meets Catchlove, he's wearing a space helmet with multiple eye holes all over it. However, the Ice Warriors have only two eyes, located in the same place as human eyes. So whom was that helmet designed for?
    • It's an old-timey diving helmet, it was meant to keep the pressure in while still being able to see in all directions. You might recognize a similar helmet on the Big Daddies from BioShock.
    • Why would some infantrymen fighting in South Africa have a diving helmet with them, though? It can't be from the Martian ship, because they would have had more advanced space helmets.
      • Friday told them they would need suits that can support a difference in pressuer and presumably there was not enough on the ship so they bought some along with whatever they needed to repair the ship.
      • Yes, but that doesn't explain why a bunch of infantrymen would have diving helmets with them to begin with.
      • Maybe a couple of their officers had plans to go searching for the HMS Childe Herold and its cargo of ivory after their term of service was over?
  • Godsacre shoots Catchlove, which kills the latter. But Catchlove was wearing a spacesuit. A metal spacesuit. Shouldn't the bullet have not gone through the armor, and instead rebounded and killed Godsacre, as he was standing directly in front of him?
    • The "spacesuit" was a converted diving suit. Those were mainly composed of tough waterproof fabric and rubber, and the modified one was still mostly that, albeit with a few extra metal plates and tubes attached.

    "The Eaters of Light" 
  • The reason the Doctor wanted to pull a Heroic Sacrifice was that, being immortal or as good as, he could keep guarding the Gate forever — whereas any of the Picts or Romans could only do it for a short while until they had to be replaced, perpetuating the precarious Legacy Character the Picts had going on until Kar failed and let the Creature escape. So… how, how the heck, is the problem considered to be solved when, oh, the Picts and Romans have gone in? How are they even still alive in the present-day?
    • Remember that time near the Gate passes very slowly compared to time outside it, and probably even more slowly when you're actually in it. Indeed, it may halt altogether on the other side when the Gate seals itself. For the volunteers who went in there to hold back the creatures, it may have only been a matter of hours since they crossed over. And the local folk appear to remember the legend of Kar, so may well be sending in more heroic volunteers - probably armed with something better than Roman swords and Pictish spears - whenever a fresh bunch of defenders is needed. In which case, they'll surely hold off the light-eaters until UNIT, Torchwood, and/or the Doctor can find a way to permanently seal the inter-dimensional rift.

    "World Enough and Time" 
  • Is Bill the first Cyberman?
    • It's unclear. The next episode reveals that by the time the Doctor and company arrive at the hospital, there are tons of Mondasian Cybermen walking the streets. It's possible that by the time she was converted, a few had already been created and she just hadn't seen them out and about yet.
    • She seems to be the first one to sport "handles". Whether that makes her the first "true" Cyberman or not, as opposed to a "proto-Cyberman" cyborg-slash-patient, may be a purely semantic question.
  • When Nardole suggested using the TARDIS to go back in time to get to Bill earlier (knowing it had been years for Bill even though only minutes for them) the Doctor dismissed this since being this close to a black hole it would be impossible to pilot the TARDIS accurately, That's fine, but why then could they pilot it accurately enough to land in exactly the right place for the distress call in the first place? Even if we suppose they followed the signal to the ship and that piloting's easier if you're not near a black hole when you leave (only when you arrive), couldn't they do that again? What's to stop the Doctor piloting the TARDIS off the ship (he wouldn't need to be accurate in where he went, he would just need to go somewhere) then using whatever method he used to land on the ship the first time to get back there, somewhere further from the black hole, but before years had passed for Bill? Given time on the ship would pass at the same speed or slower than the rest of the universe (depending on the effects of the black hole) he wouldn't need to be overly precise since he has a period of years to work with and any time earlier he arrives is an improvement.
    • Although the TARDIS definitely landed in the right place, I don't think it landed in the right time for the distress call. If I recall correctly, the TARDIS landed days after the crash (which is years for the bottom of the ship). In other episodes, the TARDIS always arrives just before catastrophe hits, but here there were already huge numbers of pre-Cybermen (the "patients"). My point is, the Doctor probably means that if he messes up the timing, by the time he gets back, there are only Cybermen on the ship. And to make matters worse, the distress call probably helped with the timing, so finding the correct time before Bill could still be saved is even more difficult than just arriving any time after the crash.
  • Some questions about the Converted taking Bill from the front of the ship down to the hospital:
    • Does time dilation affect them in any significant way when they travel up and back?
      • Not in any way that affects the plot or the Cybermen's plan. It just takes a long time from the perspective of the lower floors.
    • Have they dealt with the threat on the 507th floor mentioned by Mr Razor (or was he lying?)
      • The nature of things on the 507th are dealt with in the next episode but it's apparent that the lifts can go past that floor.
    • Why are they only collecting humans and not interested in Time Lords, blue people or Nardole? (and is it racist to call them 'blue people'?)
      • Mondas being a twin planet of Earth would have people who were more or less human. It would make sense their procedure would be human focused not Time Lord focused or Nardole focused. No, it is however racist to call them Smurfs.
      • Plus it's been part of the shows canon that Cybermen could only be made from Humans until Nightmare In Silver.
  • It's understandable that the Doctor is upset that he was too late to save Bill from Cyber-conversion, but has he considered the silver lining (so to speak) that he finally has a companion who could theoretically live forever, meaning he'd never be lonely again — especially if the business with Missy doesn't work out? She still appears to be capable of emotions, so even if he can't undo what's become of her, they can still travel together and have wonderful adventures. And his "duty of care" wouldn't be so much of an issue either; he'd effectively have a straight-up bodyguard!
    • She can still cry but she doesn't seem completely sane. Also, given her appearance, he'll have a hard time finding anywhere to take her where they're not either afraid of her because they know she's a Cyberwoman or because they assume she's a strange robot from the future. So I suspect this will still put a dampener on festivities.
      • This would be a good way for the Doctor to broker more peace and love in the universe though — teaching those scared people not to judge by appearances!
    • There's a reason the Cybermen's MO is so abhorrent. Bill might still be human enough to cry at the moment but she is in constant agony and eventually she will lose all sense of self and become an unfeeling robot who desires nothing but to inflict the same fate on others. The Doctor would at some point be forced to kill her to stop her upgrading someone else. Plus, her Cyber-form is a constant reminder of his total failure to keep her safe.
      • But he didn't totally fail — he did everything he could to save her. It wasn't enough, but doesn't he deserve credit for trying? Also, he could reprogram her to be herself again, or find someone reputable who can do so, even if the entire conversion cannot be undone.
  • Is it really hopeless for Bill? She and the Doctor love each other, and they're together again. Why doesn't he immediately start trying to overload her emotional inhibitor with The Power of Love, encouraging her to think of him and her and her mum? This would reverse the Cyber-conversion, as with Craig in "The Lodger". Or is that just being saved for the top of "The Doctor Falls"?
    • It's definitely not hopeless. Keep in mind that last year two separate characters actually died and were not just brought back but rendered ageless and eternal. A few years ago the universe was almost completely destroyed and then restored exactly as is with Big Bang 2. The Time Lords were wiped out and then they returned. Just this year the world endured six month of alien occupation and then it was all forgotten (these aren't only part of the Moffat era either, I know, right at the start of the Davies era for example had Jack Harkness die and then come back). Basically, it's become a rule that anything that can happen can also unhappen. There are a hundred possible ways that it could be written that the Doctor will reverse Bill's conversion including those you listed above, some playing with time, playing with how the process works, having the conversion revealed not to have been complete etc. Of course, even if they do save her, they were never going to do it in the first part of a two part episode.
    • In any case, Craig's fix wouldn't work for Bill, because she'd already been mortally wounded when the first of her implants was installed. Craig still had a fully-functional human body, so only needed to expel the Cyber-wiring that was invading his nervous system; Bill's heart had been destroyed outright, so rejecting the artificial parts that were filling in for it would kill her on the spot.
  • Why is the Doctor Dying Alone in the pre-credits sequence? Did everybody just abandon him? And why step out of the TARDIS when there's nothing outside but icy wastes instead of the warm glow of the console? Hasn't Twelve suffered enough without everybody being a jerk in his hour of need?
    • From an out of universe perspective, they couldn't show anyone with him without spoiling the fact that they survive all the events to come (showing Bill in particular would mean giving away if she gets saved from being a Cyberwoman). In universe, we don't know. Maybe he ran away from everyone because of the events of the coming story (or they left him). Maybe he just preferred to be outside where he couldn't accidentally hit one of the buttons in the TARDIS and send himself flying towards the sun during his regenerative throes.
    • Given the magnitude of the energy discharge with his last regeneration, he likely is afraid to regenerate anywhere near those he cares about, including Sexy's console room. Look what happened to the TARDIS when Ten regenerated into Eleven, even — she got rather blown up and crashed hard!
    • "The Doctor Falls" shows that the Doctor had tasked Nardole to look out for the colony ship's remaining humans, Bill brought Twelve back to his TARDIS where she thought he belonged, and Missy got shot by her younger self before she could rejoin him. Nobody "abandoned" him on purpose, it just worked out that way.
    • And "Twice Upon a Time", like "The End Of Time" before it, shows us why it's a terrible idea to regenerate inside the TARDIS.
  • How comes the Doctor is suddenly wary of piloting the TARDIS near a black hole to reach the lower decks? In The Satan Pit, he boasted that black holes were more or less invented by Time Lords and little more than a nuisance for a TARDIS.
    • The planet and ship from The Satan Pit were only inside a black hole's gravitational field, not its event horizon. They were being sucked in by forces too powerful for a conventional spaceship's engines to escape, but not too powerful for a TARDIS to slip through. The Mondasian ship's bridge end is practically touching the event horizon, which means the actual laws of physics are getting twisted out of kilter there: the TARDIS can no more navigate there reliably than the Time Lords could deal with Omega's power-drain by sending some TARDISes full of troops into that black hole in The Three Doctors.
  • Why didn't the Doctor just board the lifts with the Proto-Cybermen as they took Bill away? (Aside from "There wouldn't be much of a story if he did")
    • The blue guy'd just warned them that the Proto-Cybermen were incredibly dangerous. Also, the lift wasn't that big.
  • Why did the repair crew sent to boost the engines decide to remain there and begin to reproduce instead of going back up once their work was finished?
    • They probably still had hope that some other vessel would happen by and rescue them, which would only be possible at the end of the ship that was still in sync with the rest of the universe. While they waited, members of the group paired off.
  • Why doesn't Missy have any memories of being on the colony ship as the Saxon Master? The memory loss that results from incarnations meeting shouldn't be a factor here, since he was on the ship for way, way long before Missy came on board. First as the city's ruler, and then disguised as Mr. Razor for who-knows-how-long. And yet, not even that disguise creates any semblance of recognition with her.
    • It's plausibly because she either arrived just before or just after Saxon, given how large a time difference is between the floors. By the time Missy and co had landed in answer to the distress call, only 2 days had passed up top whereas 365036 days had passed below. In the time between Bill being taken away and the Doctor figuring out what was going on and following her, 1 year had passed below. Missy and Saxon's time streams could very likely have crossed, causing her not to recall.
    • It's also likely that Saxon didn't actually have to meet Missy to get his recollections scrambled: just seeing her image on the telescreen that showed what was happening on the bridge-level could be enough for the "no memories for the younger copies" effect to kick in. And he was probably watching her for months before Bill showed up at the down-level hospital.
  • Why didn't the Doctor and his other companions haul Bill into the TARDIS rather than let the Proto-Cyberman take her away after she was shot? Surely the TARDIS could immediately find a place where Bill could be fixed up, and even keep her alive in the interim — after all, the Doctor said she'd always be safe in there. Yeah, it would mean abandoning the stranded spaceship, but them's the breaks.
    • The TARDIS's medical facilities are limited, as are its capacity to deliver its occupants to a place where they can be treated. Twelve's own bout with blindness demonstrated that, as did the half-arsed job he did of reconstructing Nardole and the soccer-star kid from Class. Plus, her entire heart was freakin' gone. A ship's on-board infirmary isn't going to cut it, even on a TARDIS ... in fact, especially on a TARDIS, as anyone flying one of those would be expected to regenerate from such a ghastly injury anyway.

    "The Doctor Falls" 
  • Why was the Master so adamant that he would never stand with the Doctor? I know they aren't exactly conventional friends but they were willing to cooperate before when it suited them. In particular, "Logopolis" has them working together (until the betrayal but it didn't seem planned) and "Trial of a Timelord" had him working in the Doctor's interest, as did "The Five Doctors", albeit for his own benefit. At "The End of Time" they allied again. I understand they have different views on the universe and that this is a different situation (that the Master would be risking his life to do what was right rather than just doing something right because it suited him), but he says it with such conviction and is even willing to kill "himself" (or should that be herself?), rather than allow himself to live as a possibly temporary ally of the Doctor. Does he really hate the Doctor that much, particularly considering this is the same Master who will eventually go on to redeem himself and accept his friendship with the Doctor as Missy? Or can he just nor stand the idea of losing his identity as a "bad guy"?
    • It was probably more along the lines of him being unable to stand that Missy said the Doctor was right to be selfless. If she honestly comes to believe that, then she's essentially saying that all of their previous lives as villains have been futile: they achieved nothing, they harmed millions of people for nothing, and whatever self-rationalizations Saxon or Ainley or Delgado or any other regenerations that preceded them had used to justify their misdeeds were baseless lies. He wasn't that shocked, or even that unhappy, to have her betray and murder him; it's the idea that she's rejecting everything the Master ever believed that appalls him beyond endurance. In effect, the notion of "Good Missy" is as repugnant to Saxon as the notion of the "Evil War Doctor" had been to Nine, Ten, or Eleven, before they learned the truth about him.
    • There's also the fact that the Saxon incarnation of the Master is very petty and vindictive, even at the cost of his own life. He created the Toclafane because he knew it would break the Doctor's hearts to see humanity destroy themselves; he refused to regenerate after being shot, just because the Doctor was begging him to; he let himself get sent back to Gallifrey, even though he knew it was about to be destroyed, just to get back at Rassilon. Shooting Missy was just the last in a line of petty flipping the table moments - as far as he's concerned, he wins because no-one else does. The fact that he's (apparently) killed his future self for good is irrelevant, because in that moment, he got what he wanted (namely, to not give in and help the Doctor).
    • The fact that it's specifically the John Simm Master that would sooner destroy his future self for keeps than let her be redeemed may also be Fridge Brilliance, if you consider the circumstances under which that particular Master originated. Saxon wasn't just any old regeneration or Body Surf, but the regeneration that'd kicked off immediately after the character shed his pseudo-identity as Professor Yana. Although Yana was a phony persona imposed via Chameleon Arch, not a legitimate regeneration, he was also a genuinely good man: capable of all the compassion, loyalty and affection that Twelve had sought to instill in Missy. We hear for ourselves how much contempt and rage the Jacobi-Master's real, submerged personality had for Yana, when he hears the voice of his true nature scolding him from within the fob watch. John Simm's Master wasn't just born from Jacobi-Master's envy of the Tenth Doctor's youth and vigor, but from decades of frustration and disgust that Jacobi's submerged "Masterly" persona had felt for Yana's goodness. That revulsion only had a few minutes to express itself as Jacobi before Chantho killed him, but his loathing helped shape Simm's proclivities as his new self arose. Now, at the end of Simm's life, Missy's telling him the unthinkable - that she's voluntarily adopting the same principles he'd been born despising - and it's absolutely unbearable to Simm. The idea of becoming Good again, perhaps permanently, would run counter to the very foundation of Saxon's individual quirks and proclivities, far more than to any other Master before him.
  • The Doctor says he "Expanded the Definition of Humanity" by changing a 1 to a 2. Wouldn't that just change the definition to only include Time Lords (expanding the definition would mean changing it from "find someone with one heart" to find something with "less than or equal to two hearts", unless they were previously looking for something with "less than or equal to one heart")? Shouldn't the Cybermen lose interest in children with only one heart and instead target Time Lords only? I know it's possible the "weapon's grade" Cybermen would attack indiscriminately anyway but before that one arrived the Doctor had no reason to believe it wouldn't be the standard Cybermen showing up that he'd just reprogrammed, and if they'd only target Time Lords then going somewhere else and leaving the humans be would have seemed the safer option for the humans.
    • They probably did stop gathering humans to convert for a while, but the Cybermen were still working with human surgeons at the time. Probably the Cybermen temporarily walked away from their human-conversion duties to try to round up the Masters and Doctor, but their human co-conspirators realized something was wrong, checked the software, and found and corrected the Doctor's tampering. (Remember that plenty of human residents of level 1056 want to become Cybermen, as they're dying already and are Conditioned to Accept Horror.) The Cybermen which Saxon points out leading children to the hospital hadn't yet received the software update incorporating the Doctor's hack, which Twelve specifically stated would take a little while to upload.
      • Would that mean they stopped targeting Time Lords then? I suppose it's possible they would have ignored The Doctor, Missy and The Master later in the episode if they weren't in their way/didn't attack and we just didn't see it.
      • The Expanded Universe short story "Alit in Underland" (The Missy Chronicles) explains that during the two-week Time Skip, the two Masters (with Alit as a Tagalong Kid) snuck onto lower floors, successfully undid the Doctor's reprogramming, and came back to 507. The Doctor was still unconscious at the time and one can assume he never knew they did this. Incidentally, it's also established that it's during this mini-adventure that Missy decides she'll have to kill Saxon at some point so she can stand with the Doctor.
  • Was there a minimum amount of crying Bill had to do before Heather could show up? Being near the blackhole can only mean that time in going slower where they are than the rest of the universe (generally speaking obviously, given as they say time is relative) which would seem to suggest Heather should have, from their perspective, a faster travel time. However, in "The Pilot" she was able to travel anywhere in moments. Weeks passed during the story and in fact Bill had even shed tears before it started. If it was her tears that brought her there, shouldn't Heather have shown up at the start of the story rather than the end? Or was a bit of crying not enough and Bill really had to go for it before Heather could show up? Presumably if Heather had known Bill had gone through Cyber-conversion she would have come straight away to help rather than waiting until the story was over.
    • There's a big difference between a little crying and a whole lot of it. Pilot-Heather could probably tell how hard Bill was weeping, and came this time because it's much worse than on previous occasions. Alternately, Pilot-Heather may have been popping in to check up on Bill all along, disguised as ordinary puddles, glass, or whatever every time she cried, but only chose to intervene this time because Bill was truly in despair and the Doctor'd already failed to restore her.
      • The latter theory appears confirmed by an Expanded Universe comic book story, "The Great Shopping Bill" (Doctor Who (Titan)): in a throwaway bit Heather, unnoticed by Bill, appears in a tide of spilled soda and actually says "Just keeping an eye on you, Bill Potts."
  • How come with 2 weeks to mull it over, the Doctor hadn't figured out how to fix Bill? That would be a lot of time to ponder places they could go (reputable sawbones, clone facilities, etc.) once they got back to the TARDIS. Come to think of it, why isn't returning to his TARDIS a priority for the Doctor in the first place, since he knows how much Bill is suffering and her fate was the unintended result of his good intentions running up against a bad situation and his not realizing how bad the situation was? Isn't his duty of care to someone he knows — especially after what happened with Clara — more important than the welfare of people he doesn't, especially when even he admits their situation is near-hopeless? Maybe the Doctor needs treatment for the whole Chronic Hero Syndrome thing...
    • I agree the Doctor shouldn't have had an issue figuring out a way to treat Bill given the technological precedents set in the show (given death itself has been reversed once using devices which just happened to be available in "The Girl who Died" and Moffat's own "Empty Child/Doctor Dances" showed the possibility of alien nanogenes turning humans into gas mask monsters in seconds, reconfiguring the human body doesn't seem to be particularly difficult with some of the advanced technology out there, not to mention we've seen stuff like android bodies and consciousness transfers). However, given Bill's life wasn't in danger, and given time was passing much more slowly where the TARDIS was (meaning the Cybermen could catch up with them quickly once they arrived there) the Doctor wasn't unreasonable for trying to save these people and deal with the Cybermen rather than just trying to make a run for it and let people die unnecessarily. Also, there's no reason why his duty of care should be greater to someone he knows. A life isn't more important simply because it's a life of a friend and saving Bill at the expense of the children wouldn't undo what had happened to her but it would result in the death of the children, but if he didn't save her and saved the children then it's still just one life against many. Meanwhile if he saved everyone, which is obviously what he hoped, that was the best outcome.
      • Bill showed she was willing to die for others when she agreed with Missy that her own brain-death would be an acceptable price to pay to drive the Monks off of Earth. If the Doctor were to abandon a bunch of children to the Cybermen to preserve her life now, when said "life" is an And I Must Scream existence, she'd probably be less forgiving of that than of his failure to get to level 1056 and prevent her upgrading.
    • In a related issue: Why doesn't the Doctor make a Heroic Sacrifice and give the regeneration energy he's holding back to Bill to undo her Cyber-conversion? This would allow him to both die peacefully as he wants to and ensure his companion won't have to face a Fate Worse than Death. Of course, thanks to Plot Armor the Doctor can't straight up be Killed Off for Real, so a miracle could kick in just in time to allow him to keep living.
  • So why is that the Doctor is struggling to halt his regeneration? The Master managed to stop regenerating at all out of spite and yet the Doctor's regeneration keeps starting despite his efforts to stop it.
    • Presumably it is possible to hold back regeneration but it's just hard. The Master may have simply been better at doing so.
    • My theory is that The Master was content with dying, while The Doctor doesn't was to die. He's trying to stay alive while also trying not to regenerate.
      • More like the Master was content with letting his body die, because he knew his brainwashed followers were waiting to bring him back (which they did, in "The End Of Time"). He therefore had no fear or doubt to hold him back, unlike the Doctor, who could still sincerely confess that he fears dying even after billions of deaths in "Heaven Sent".
    • It's also possible that holding back regeneration completely results in death. That's how the Master did it, but the Doctor doesn't want to die or regenerate, so he has to 'let out the pressure,' so to speak, in order to keep going. Before the end of the Christmas episode he will have to choose to change or die, and we know he ain't gonna die.
  • Exactly where did the farmers on Floor 507 come from, especially the orphans, considering everybody on this ship was the offspring of the crew of 20 who went down to boost the engines in the first place?
    • Razor/Saxon mentions a previous expedition to that floor which had never returned. Everyone back home assumed they'd been killed by something horrible, but presumably they just realized that the solar-farm level was a lot better place to live than Floor 1056. If it took them a while to catch on that the Time Dilation effect was happening, hundreds of years would've passed on Floor 1056 before they were ready to go back, so they'd know there weren't any loved ones waiting down below. Fast-forward a few hours of Floor 1 time, and the lost expedition's handful of members have bred up their own agricultural society.
    • The children weren't orphans, they were the kids of the people we see defending the farm. The residents of 507 had gathered all their children in one place to better guard them from the proto-Cybermen.
  • What triggered the Doctor's regeneration? Many can assume that the electric hug from the Cyberman triggered it, but it really doesn't explain why Missy asked the Doctor about his health in "Empress of Mars", implying that his regeneration started before. Was it oxygen deprivation from space in "Oxygen"? Or Bill accidentally shooting the Doctor with real bullets in "The Lie of the Land"?
    • I'm pretty sure the one trooper who forgot to switch his bullets for blanks was not the one Bill stole the gun from. Missy could simply have asked the Doctor about his health to mess with him since he looked so surprised to see her at the controls and ready to go back into the Vault. Otherwise, the 12th Doctor did not have a really restful life, especially in this season (and what happened in Heaven Sent may have also left a mark), so his body may simply have been wearing thin like the First and War Doctors.
      • I think it might actually be a combination of that mixed with the Cyberman's electric hug. The attack itself shouldn't be responsible on its own, or else the Doctor would've regenerated involuntarily while he was unconscious. I think that you're right in that his body was beginning to wear thin by this point after all the hell this incarnation has been through (which Missy noticed, hence her line abut his health). But then, the injuries he sustained first from the Masters assaulting him and then the Cyberman attack sped up that process and left him on the brink of regenerating much sooner than he should have been.
    • It was the electric hug. Missy's comment about the Doctor's health and Bill shooting the Doctor only for him to ultimately be okay is just Foreshadowing.
  • Given that an excess of emotion can undo Cyber-conversion, as seen in "Closing Time", and Bill's emotions are strong enough to activate her headlamp beam (and her mind was previously strong enough to override that of the Giant Monk), why didn't the Doctor encourage her to turn her emotions inward to regain her human form — thinking of her love for the Doctor, her mum, etc.?
    • Craig still had a complete and functional human body, just one that'd been invaded by Cyber-implants. Bill's entire heart was vaporized, such that only the proto-Cyber technology had kept her alive for the last ten years: had she mustered the emotional effort to reject the implants, she'd have dropped dead on the spot.
      • This makes sense, but once again raises the question of why the Doctor apparently didn't think to give her the regeneration energy he was holding back, since that could have restored the missing body parts.
      • Because honestly, that could've created another Time Lord-human meta-crisis.
      • Which would have been a bad thing under the circumstances why? Any extra help in a storm...
  • What's with the Double Standard regarding Bill and the Doctor? Both would rather die than accept their Cyber-conversion/regeneration, respectively. But while Bill being restored to humanoid form by Heather is seen as wonderful, the Doctor isn't similarly rescued and the point of the forthcoming Christmas special is that he has to accept a painful, forced regeneration and Loss of Identity. And while Bill comes out even better for her restoration, becoming like Heather with the same powers, the Thirteenth Doctor will get, as it turns out, a Gender Flip that will make it harder for them to be taken seriously, given how society treats women. Why does the Doctor have to suffer but not Bill?
    • Well, not to spark an argument, but that's a rather subjective argument that the Doctor changing gender is a form of "suffering". Despite societal differences in how men and women are treated, the Doctor's always had issues being a voice of authority but eventually manages to coerce people to listen to them, and being a women probably won't change that dynamic very much in the log run. But anyway, a forced regeneration is how the Doctor carries on living anyway. It's how he's always been able to carry on, and as he'll probably have to learn in the Christmas special, it's a much-preferred and ultimately much more hopeful alternative than simply dying away as himself. And besides, while Heather was able to resolve Bill's form, she probably couldn't do the same for the Doctor, with his more complicated Time Lord biology necessitating that he regenerates, and her lack of an emotional connection to him. In the end, there is no Double Standard, because Bill and the Doctor will be in the same place: rejuvenated into a new life, but with the same purpose and same hopefulness they've always had carrying them forwards.
      • I meant suffering in the sense of the forced change rather than the Gender Flip, but this argument makes some sense — except that Bill also could have had a new life yet with purpose and hope even if she stayed a Cyberman. This would have been a more equal playing field between her and the Doctor, because neither would be happy for changing and the Loss of Identity but would learn to make the most of it by latching on to their core values and turning their changed form to their advantage. Then again, the Christmas Episode can always amend this (i.e., Bill decides to be a Cyberman again — albeit a good one — to give the Doctor moral support in his time of need). But it didn't...
  • Why is Heather/the Pilot suddenly able to talk in coherent sentence and generally act as a friendly sapient being? Last time we saw her, while still emotional, she has suffered pretty massive Loss of Identity and only had her love and promise to Bill to cling onto — otherwise she was just a barely-sentient monster who could only parrot other people's words. What happened to turn her into Ashildr 2.0?
    • As noted above, the Expanded Universe has confirmed that Pilot!Heather kept watch over Bill and her travels, which was 11 years or so from Bill's perspective (taking into account 6 months of Monk rule, 10 years in the Mondasian city, etc.). The Power of Love would seem to have helped her reassert her identity over time. Moreover, because Pilot!Heather is a time-space traveller, many, many more years may have passed from her perspective...
    • Given that much time to prepare, the Heather-pilot could probably just find the means to learn better methods of communication with humans, be it by download or study. Heck, she and liquid-Bill might not be speaking words at all; they could be communicating via some means unique to Pilots which Bill perceives as speech, same as she saw herself as human after the Cyber-conversion.

    "Twice Upon a Time" 
  • So why doesn't Twelve remember One not wanting to regenerate, meeting up with Twelve, and the choosing to regenerate after all? The question is raised during the episode, but unlike with other multi-Doctor adventures, there's not even a Hand Wave to explain why the Doctor doesn't remember any of the things that happened to his previous incarnation.
    • Because any time a Time Lord meets a different regeneration of themselves, it's a minor paradox that results in the younger version's memories getting scrambled. It's been mentioned in several multi-Doctor stories; only the eldest copy remembers the event fully. The only odd part here was that Twelve didn't remember the event at all when usually he'd have some vague memory (ie, in "The Time of the Doctor" Eleven didn't remember meeting himself while he was Ten, but he knows he married Queen Elizabeth), but that's not a big deal. It was a confusing time a very long time ago even discounting the scrambled memories.
  • It's a bit unclear what would've been the ultimate fate of Captain Lethbridge-Stewart if the Doctor hadn't interfered... The Testimony are supposed to pick up a person right before they die, but if the Christmas Truce was always gonna safe his life, why did they choose this moment to transport him? However, if he was originally supposed to die before the Truce, and the Doctor actually altered the timeline to save him, why isn't the Doctor concerned about the paradox this would cause, as those kind of paradoxes have threatened the universe several times before (such as in "Father's Day", "The Wedding of River Song", and "Hell Bent")?
    • The Doctor interfered to have the Truce save his life. He's always been mostly unconcerned with minor paradoxes; it's only when things get complicated that paradoxes become a serious danger. In "Father's Day" the Doctor and Rose were visiting the same place twice (a paradox) when Rose saved her father (another paradox) and then Rose touched her infant self (yet another paradox). In "The Wedding of River Song" it was a fixed point in time caused by two Time Lords interacting at a still point, where fixed points are easier to create. In "Hell Bent," the paradox spanned billions of years; it's repeatedly implied that if the Doctor had been able to pull Clara out earlier, the universe would have just snapped back and recovered from the minor paradox.
    • As far as the paradox is concerned, the Doctor has some kind of Time Lord sense that allows him to 'know' when something is a fixed point and when it isn't, and how the timelines will progress due to a decision he or someone else makes in a moment in time. So he probably knew that saving Lethbridge-Stewart's life wouldn't cause a paradox.
  • The Doctor claims that he 'adjusted' the time-frame of the Captain's return, by returning him to the battlefield a few hours later, just before the Truce was supposed to begin. That does beg the question though - what does the German soldier remember about those few hours once time resumes? If, from his perspective, the Captain disappeared, then why would he still be at the trench? Or was everyone in the vicinity of the battlefield frozen in time for those few hours?
    • Presumably he just moved that one crater forward a few hours. Most of trench warfare was one huge bloody stalemate; no one would notice two soldiers disappearing from time for a few hours.
    • Clearly neither the English nor the German troops back in the trenches could see what was happening in the crater: if they could, each side would have presumably tried to rescue its endangered man and/or sniped at his opponent.
  • Why does Twelve finally decide to regenerate, especially after the "empty battlefield" speech? Yes, the Testimony (via Bill and Nardole) tells him he's needed, as does the TARDIS, and he does agree with the latter that the universe's residents will likely screw things up on their own. But it's practically a running theme in Twelve's tenure that his kindness and selflessness and need to save others has not brought him a lot of personal happiness; Series 9 saw him unjustly suffer for billions of years over it thanks to the ingratitude of Mayor Me, the Time Lords, etc. Series 10 saw his efforts to redeem Missy come to nothing, as far as he knew. Why does he (or, now, she) want to prolong his suffering for ungrateful "mortals"?
    • Because of his kindness and selflessness. Ultimately he's still the Doctor, and prolonging his life in part to help others even if they aren't always going to be grateful for it is what the Doctor would do. If he was the kind of person who'd do the life-renewal equivalent of taking his ball and going home because people didn't appreciate him enough, he wouldn't really be the Doctor in the first place. Besides, like the First Doctor, he's come around to the idea that it's not fair to deprive his potential future selves their chance at existence because of his own issues.
  • Why can Testimony-Bill remember the Pilot's visit? By the time Bill noticed Heather in The Doctor Falls, her Cyberman body was already dead; it was another copy of Bill's consciousness, one embodied in the Pilot's "not-water", that saw her. So, what, did the Testimony people arrive a second too late, see the human body was dead, but that the consciousness lived on in watery form right next, and… do the next best thing? Regardless of how ridiculous that sounds in the first place, why would they bother to Mind Upload the memories of Water-Bill even though her sheer existence basically meant the Testimony had had their job done for them by the Pilot?
    • All There in the Manual: The Paul Cornell novelization explains that the Testimony temporarily removes the memories of Bill's avatar beyond the Pilot's arrival because it needs her to interact with the Doctor as she did when they were together to best judge whether he is good or not. After that's determined, she's given ALL of her post-"The Doctor Falls" memories back: she and Heather traveled the stars, eventually settled down on Earth as humans, and grew old together; Bill ultimately decided to die as a human rather than become a Pilot again, but not before telling Heather she could and should return to that state. That was when the Testimony stepped in to harvest all of the memories of Bill Potts.