The Doctor Falls (TV story)

The Doctor Falls was the twelfth and final episode of series 10 of Doctor Who.

It saw the departures of both Bill and Nardole, and the apparent end of the Master's life. Expanding on the Twelfth Doctor's regeneration teased in the previous episode, it saw him mortally wounded in battle against the Cybermen. The regeneration would also begin twice, both of which he managed to postpone, however, as the Doctor refused to change, having grown accustomed to being in his current incarnation, mirroring the First, Second and the Tenth Doctor's attitude towards the process. Furthermore, the Twelfth Doctor had also expressed he was sick of "always having to be someone else"; reflecting on how the Doctor has become tired of regeneration, having changed many times.

The episode also shows the events leading to 's regeneration into, with the male Master being mortally wounded by his female successor, and he in turn seemingly killing her, presenting how (unlike the Doctor who has teamed up with his past and future incarnations and has gotten along with each incarnation he's encountered) the Master rarely works with any of his other incarnations as he would eventually double-cross himself. Having displayed how the Master had regenerated into Missy, the episode marks the last appearance of John Simm as the "Harold Saxon" incarnation of the Master in his natural stream of events. Missy's fate, and as a whole the Master's fate, is unknown, and with Michelle Gomez's announcement that she was stepping down from the role The Doctor Falls marks her last appearance as Missy.

The finale also shows that, while Time Lords don't retain a conscious memory of meeting their past or future incarnations, it is possible for their subconscious to retain certain thoughts and ideas. Notably, the Master had a hand in creating this branch of Cybermen, and though Missy didn't remember this, she was inspired to create her own army out of dead humans back in Series 8.

Missy's existence presented as a time loop; if the Doctor had not chosen this ship to test her newfound goodness, she would not have been able to give her past self-help to escape or mortally wound him to ensure he regenerated into her. As such, if Missy was not around, the Doctor would not have met Clara Oswald. The story featured several connections to the 1966 serial The Tenth Planet, including a story featuring humans from Mondas, and featured appearances by the Cybermen from said planet. Most notably, the episode featured the unexpected return of the First Doctor, now portrayed by David Bradley, in a scene set during the events of The Tenth Planet itself, the first time an incarnation of the Doctor from the classic series has appeared since the series was revived in 2005 (excluding the mini-episodes Time Crash and The Night of the Doctor and the use of archive footage). Bradley had previously portrayed William Hartnell in the docudrama An Adventure in Space and Time.

The episode explained that the Cybermen take on different appearances due to "parallel evolution"; even though the Cybermen are descended from Mondasians, they came into existence in different parts of the universe.

Synopsis
As he struggles to resist regenerating, the Twelfth Doctor prepares to make a last stand against the ever-growing army of Cybermen. However, with Bill still a Cyberman, and gradually turning to her old wicked ways as  reminds her of who she used to be, can the Doctor convince his old friend to finally be good before he falls?

Plot
The episode opens to a group of farmers, adults and children, on Floor 0507 facing against the prototypes from Floor 1056, dubbed "scarecrows", shooting them down by night to then restrain them on wooden crosses by day. A school child is out in the field one morning when a shuttlepod blasts through the ground, crash landing near her. From the rubble, a Cyberman walks out carrying an unconscious Doctor.

Sometime earlier, the Doctor awakes on top of the hospital, now restrained in a wheelchair, soon recalling how he was subdued by and. The Master and Missy dance and flirt, with him asking if she's his next incarnation; Missy guesses she is as she can't remember what caused her to regenerate. The Master is stunned: "I'm going to turn into a woman, and you can't remember it happening?" Missy wonders if she is a woman; the Master confirms it. Though the Master doubts it, the Doctor begins deducing what he's been up to since he vanished while blasting Rassilon with his life energy.

Upon getting back to Gallifrey, the Time Lords, grateful for the Master's help in preventing Rassilon from executing The Final Sanction, properly restored his body. With that done, the Time Lords kicked him off Gallifrey. However, the Master stole a TARDIS to go back into the universe; so he considers it a mutual being kicked out. After that, the Master landed on the colony ship, lived like a king and killed people at his leisure. However, the colonists eventually overthrew him and the Master attempted to flee. However, as his TARDIS was on the last level, too close to the event horizon, it burned out his dematerialisation circuit and left him stranded. "You never could drive could you?" the Doctor asks.

Both the Master and Missy are insulted; she asks her earlier self if he has any requests as to how to torture the Doctor. The Master suggests dropping the Doctor off the roof; Missy is against the idea, saying that they'd be "up and down the stairs all night" cause she doesn't know how many regenerations the Doctor has. Missy and the Master look over the roof, seeing people march like mindless sheep into the hospital to be turned into Cybermen. They taunt their old friend by telling him of their plan of the Cybermen converting all the humans on the ship. Missy asks the Doctor if he's impressed. They mockingly call the Doctor "granddad", reminding him that Bill is now a Cyberman.

The Doctor tells them that after all this time if they still think they're winning when he's in the room, they're missing something obvious. Hearing the Cybermen advancing, Missy looks over the ledge and quakes in horror; the Cybermen are coming for them. The Master is confused, as these Cybermen are primitive and shouldn't even be attempting to convert non-humans.

The Doctor explains that when he was knocked down by Missy, he altered the signal of the Cybermen so they would convert two-hearted beings as well, hence why they are now focusing on the Time Lord's presence. The Masters panic, Missy frantically using her sonic umbrella to lock a metal door to hold back advancing Cybermen while the Master uses his laser screwdriver to destroy advancing Cybermen. The Doctor brags that he is the only one who is able to stop so many Cybermen at once. Realising this, a conflicted Missy knocks the Master out and frees the Doctor from his restraints. The Doctor starts wondering which side she is on to which she admits her indecisiveness as she is confused and her other half is unconscious.

The Doctor uses his sonic screwdriver to contact Nardole, who reveals he has commandeered a shuttlecraft. Nardole lands near the roof to help escape, but the Doctor is grabbed and electrified by a Cyberman before he boards. Missy tries to save him using her other self's laser screwdriver but Bill, in her cyber form, intervenes first, destroying the Cyberman with a blaster based on her head. Missy and the Master try to convince Nardole to abandon the Doctor "The Doctor's dead; he told me to say he always hated you," they both say. However, Bill prevents the shuttle from leaving, grabbing the ladders until they rescue him.

They escape to Floor 0507, where time moves slower. They find themselves on a solar farm, the Master deducing such by the holographic sky, where some of the humans and a large number of children protect themselves from the early Cybermen prototypes from Operation Exodus. Nardole approaches the girl, declaring they will need her help. They spend two weeks there while the Doctor recovers from his injuries.

Bill awakes in the barn, unsure why the villagers are scared of her, concerned why she can't see the Doctor. When given a mirror by a child, she becomes horrified to discover she was converted into a Cyberman. The girl goes to run but bumps into the Doctor who thanks her for being kind to Bill, offering her a jelly baby as she leaves. The Doctor has somewhat recovered, though he still has a scar from where he was hit by the Master.

Trying to console Bill, she gradually realises that though she thinks she is human, she is still a Mondasian Cyberman in appearance. She grows angry, the Doctor backing away as Bill accidentally triggers the blaster on her head, igniting the door on the barn, causing an explosion. Nardole, who has been preparing the town for the oncoming Cybermen despite one woman saying he has been working them too hard, passively tells the farmers not to worry; they have an upcoming war to focus on.

Bill sheds a tear when she realises the humans are frightened of her, and the Doctor wipes it away, noting it unusual. The Master tells the Doctor that he and Missy have been working on something, and pauses briefly to mock Bill, chastising the Doctor for still referring to her as a female and taunts how he hated the time he had to spend with Bill as "Razor". He stops because Bill claims he is not upsetting her, though she cries beneath her mask when he leaves. The Doctor finds it odd she is still able to shed tears. While traversing after the Master, the Doctor struggles to walk, limping heavily. He briefly stumbles against a tree, regeneration energy attempting to trickle from his hand (revealing that his electrocution by the Cyberman on the roof was fatal, and his body is preparing to regenerate). Wanting to not worry Bill, he draws up a stick and carries onwards but Bill is still distraught that the Doctor can't fix her current condition, the Doctor responding "where's there's tears; there's hope."

They soon reach the middle of a forest, just after the Master and Missy theorise they can't retain their memories as their timelines are out of sync. Missy briefly displays empathy for Bill's condition, something the Master finds disgusting. Missy reveals she has discovered a camouflaged lift in the nearby forest, with which she suggests they can escape to Floor 0000, using her sonic umbrella to call it. However, the Doctor declares that there will no doubt be a Cyberman in the lift waiting to find their floor, as the lift was taken to the bottom by them previously. Understanding this, Bill orders them to stand aside, the Doctor convincing the two Masters to do so.

The three Time Lords prepare behind Bill, drawing their respective devices. As guessed, the lift brings up an advanced Cyberman from the lower floor, Bill speedily firing on it with her cyber blaster, the Master following likewise with his laser screwdriver as the Doctor and Missy use their sonic devices to slow its advance with a barrier. After several seconds, they disable it.

With their position given away, the Master and Missy both wish to use the elevator to go to the bridge and escape in the Doctor's TARDIS, but the Doctor informs them that the time differential between top and bottom of the ship would give the Cybermen ample time to stop them, meaning there isn't a safe way to return to the TARDIS. The Doctor figures that the Cybermen will now have much more time to plan, given they now know what floor they reside on, they must prepare for a battle. He returns to the village, revealing the alarm they now hear is the Cybermen's warning from the lower floors. Using a computer, Nardole discovers that the floor below this one has many fuel pipes that he can detonate as weaponry against the Cybermen, briefly testing such by blowing up a windmill, stunning the villagers; the Doctor remarks that they can use such to confuse the Cybermen and make them believe they are stronger than them. The Doctor finds a conduit to another solar farm on a higher floor that can be used to evacuate the children, having Bill blast it open, knowing this is a fight they will likely lose.

Meanwhile, the Master and Missy decide to leave and plan to find the Master's TARDIS at the lowest floor, though the Master reveals he broke his TARDIS. Missy convinces her younger self to always keep a dematerialisation circuit on hand. She recalls the time a woman shoved her against her a wall to convince her to carry the device on her at all times. While recalling the story she shoves the Master against the wall, revealing herself as the one to convince the Master to carry the circuit. The Master hints at a slight sexual arousal of his future incarnation, but Missy just retorts that it's very wrong. Night falls, the Doctor standing guard outside the house. Inside, a woman attempts to flirt with Nardole as he works on his computer, only to turn around and shoot at Bill, falsely thinking her a hostile Cyberman. She leaves distraught, going outside to find the Doctor. The first wave arrives, Nardole and a girl preparing to combat them, successfully tricking them that an apple was capable of destroying an entire group of them. They retreat to the house, now understanding the Cybermen will likely return to outright destroy them next time rather than merely capture them for conversion.

Meanwhile, the Doctor notices the two Masters trying to leave and runs after them. He pleads for them to be by his side to help. He gives an emotional and passionate speech on why he helps people, since it isn't easy or always going to work, it is just the right thing to do, as saving people would just be kind. The Master ridicules the idea, saying that he didn't listen to a word the Doctor said. However, Missy was somewhat moved by the Doctor's speech, agreeing that being the Doctor's friend was what she always wanted. However, after briefly grabbing each other's hand, she sides with her predecessor. At the lift, Missy tricks the Master into dancing with her and fatally stabs him, forcing his next regeneration, though she makes the wound "precise" so that the Master will have enough time to reach his TARDIS before regenerating.

Gradually dying, the Master compliments her, glad they haven't lost their touch. Missy tells her proud past self that he deserved nothing less than her best. After helping him into the elevator, Missy announces she will return to help the Doctor, turning to walk away as her predecessor shouts at her to not go. Missy tells her past self that this is where all the scheming, killing and egomania has led them: standing with the Doctor.

Unable to accept that his future self will side with the Doctor, the Master draws and fires his laser screwdriver at full blast, causing Missy to collapse on the ground, fatally wounded. He claims the strike has disabled her regeneration, commenting that it is the perfect ending, with them both shooting themselves in the back. They both laugh as the Master descends in the lift and Missy seemingly dies.

An initial wave of Cybermen arrive, but using Nardole's tricks with the explosives, they are able to make the humans appear more powerful, forcing the Cybermen to retreat and develop a new plan, giving the humans more time. Back at the house, and against Nardole's protests, the Doctor downloads the plans for the floor into his sonic screwdriver and sends him to help evacuate the children, intending to stay alone to fight the Cybermen. Nardole resists, having deduced the Doctor is going to commit suicide by detonating the entire floor in a last-ditch attempt to destroy as many Cybermen as possible. The pair argue over who really should die, Nardole reasoning he can't, given how he was before meeting the Doctor even though the Doctor tries to reason that he should stay as he is already dying. The Doctor eventually convinces Nardole that helping the children will be his penance for the crimes he committed before they met, as he is the stronger of the pair. Nardole jokes he will name a farm after him. Bill also insists on staying with the Doctor despite Nardole trying to tell her otherwise. As he leaves with the humans, Nardole admits that he will never be able to find the words for Bill and the Doctor's sacrifice.

With all the humans evacuated, the Doctor and Bill prepare for a last stand, each deciding to charge into opposite ends of the forest. Bill says one last goodbye to the Doctor, even joking briefly about her sexuality, assuring him she had still retained her humanity. They face the oncoming wave. The Doctor ignites several of the Cybermen, listing the numerous times he has defeated them while doing so. However, he is inevitably surrounded and receives a full strike from one Cyberman's laser beam. He declares he is the Doctor but the Cybermen retort they have no need for a doctor anymore, firing at him again. Falling to his knees, he prepares to ignite the floor but is struck again, the blast proving fatal enough that his body attempts to regenerate. Refusing to give in, he holds it back and ignites all the pipes below the floor, engulfing it all in a wave of destruction, destroying all the Cybermen.

Above on floor 0502, Nardole waits outside of one of the lifts, hoping the Doctor and Bill will return, however, the children convince him to move on and focus on living with them now.

Back downstairs, the floor is now a wasteland scattered with destroyed Cybermen. Bill, barely functioning but with her personality mostly restored, finds the Doctor severely wounded. She mourns over the Doctor's body but suddenly finds herself out of the Cyberman suit, seemingly human. She looks up and sees Heather, emerging from a nearby puddle. To prove to Bill that she isn't dead, she and Heather share a passionate kiss, when Heather reveals she converted Bill to a form of being like her. At Bill's request, they take the Doctor's body to his TARDIS, and Heather, as the Pilot, sets the controls for the TARDIS heading to a new location, while offering Bill the choice to return to her old life or to live out a new one with her, travelling the universe. Before leaving, Bill sheds a tear on the Doctor, but does not wipe it away, saying "Where there's tears, there's hope." She walks over to Heather and the reunited lovers walk out of the TARDIS into space, off to travel the stars.

The Doctor's wounds heal as he dreams of Bill and Nardole, yelling for him. He then dreams Rose Tyler, Martha Jones, Captain Jack Harkness, Donna Noble, Madame Vastra, Jenny Flint, Sarah Jane Smith, Amy Pond, Clara Oswald and River Song calling out his name. Twitching, the Doctor then dreams saying his name and he awakes, gasping for air. Seeing that he's begun regenerating, a confused Doctor mumbles some of the last words of his other incarnations. Yelling "No!" with all his might, the Doctor suppresses the complete regeneration. "I can't keep on being somebody else" the Doctor cries out as the TARDIS lands.

He tells his TARDIS that it doesn't matter where it's taken him; he won't listen to whatever kind of lesson that it's trying to teach him. The Doctor steps outside into an arctic landscape. Out in the snow, the Doctor resists the process screaming and shoves his fists into the snow, again stating he will not change.

Suddenly, in the distance hears a voice stating the same words of not changing, finding the idea ridiculous. The Doctor calls out, asking for the person to identify himself. The stranger asks for the Doctor's identity, which he confirms. The stranger replies that while the Doctor may be a Doctor, he is "the Doctor. The original, you might say". Much to the Doctor's shock and surprise, the stranger steps forth to reveal himself as his first incarnation...

Cast

 * The Doctor - Peter Capaldi
 * Bill - Pearl Mackie
 * Nardole - Matt Lucas
 * - Michelle Gomez
 * - John Simm
 * Hazran - Samantha Spiro
 * Alit - Briana Shann
 * Gazron - Rosie Boore
 * Rexhill - Simon Coombs
 * Heather - Stephanie Hyam
 * Voice of the Cybermen - Nicholas Briggs
 * and


 * The Doctor - David Bradley

Uncredited

 * Bill (as a Cyberman) - Liam Carey

Culture

 * Nardole shouts "Remember the Alamo" when getting the farmers to work.

Cybermen

 * The expedition to Floor 0507 appear to be used as scarecrows.
 * The very first original Mondasian Cybermen can electrocute people by hugging them tight, and shoot death rays via their head lamps on their emotional inhibitor.
 * Nardole tells the farmers about Operation Exodus.

Technology

 * The Doctor changes the encoding in the Cybermen's system from reading one heart life forms to reading two hearts.
 * The Doctor says that parallel evolution is the reason for various civilisations evolving Cybermen.
 * Missy says Bill is doomed to live as a bio-mechanic psycho-zombie.
 * The Doctor mentions sewage and smartphones as inevitable.
 * The Doctor says the internet and cyberspace are a result of people plus technology minus humanity.
 * The Doctor says it took the Cybermen a while to update the net to track two-hearts instead of one-hearts.
 * The Master and Missy use their laser screwdriver and sonic umbrella, respectively.
 * The Doctor can use his sonic screwdriver as a microphone.
 * Nardole pilots a shuttle labelled SL-16.
 * Nardole uses a computer.
 * Missy carries a dematerialisation circuit because of a scolding she gave herself.
 * Nardole says that under the floor of the farm there are fuel lines and fusion turbos.
 * The Doctor mentions the farm's cryogenic chamber.

Biology

 * The Master and Missy talk about their regeneration.
 * The Doctor again displays a degree of control over his regenerative ability.
 * Nardole implies he is a cyborg.

Food and beverages

 * Missy calls the Doctor a "silly sausage".
 * The Doctor offers Alit a jelly baby.
 * Apples are used as grenades in the deception.
 * Heather mentions chips.
 * Bill mentions tea.

People

 * Bill asks the Doctor if her tear is engine oil.
 * Heather the oil creature returns for Bill and removes her from her Cyber-suit.
 * Missy puts on lipstick.
 * Missy calls the Doctor Mister Volcano, because he's internalising.
 * Missy calls the farmers the Waltons.
 * Nardole was a black market dealer once.
 * The Doctor uses mathematics to conclude he can't go to the TARDIS
 * The Doctor mentions Donald Trump as inevitable.
 * The Doctor likens Bill's strong resisting mind to a perception filter.
 * The Master and Missy high five each other.
 * The Master and Missy dance with each other.
 * The Master practises applying eyeliner.
 * The Master thinks about getting inappropriate with his older female self.
 * The Master calls Bill Robo-Mop.
 * The Master calls Missy "sis" and "Lady Version".
 * The Twelfth Doctor meets the First Doctor.
 * Missy creates two bootstrap paradoxes; one by telling her former self to always carry a spare dematerialisation circuit, two by creating herself by killing her predecessor.

Species

 * The Doctor refers to the Monks' invasion.
 * The Doctor says that Cybermen have monkey brains.
 * Nardole says he will name a pig after the Doctor.

Locations

 * Floor 1056 has already been converted and invaded by Cybermen.
 * The Doctor remembers being knocked out in the Conversion Theatre.
 * The Doctor recalls the Master on his way to Gallifrey.
 * The Master says the hospital has been turned into the Cyber Foundries.
 * The Doctor mentions Mondas, Telos, Earth, Planet 14, Marinus, Voga, Canary Wharf and the Moon.
 * Floor 0507 is a solar farm.
 * The Doctor, Nardole and Cyber-Bill protect a village on Floor 0507.
 * The Cybermen are seen flying past Floor 0900.
 * The Doctor says there's another solar farm on Floor 0502.
 * The TARDIS takes the Twelfth Doctor to a snowy landscape to deal with his change, along with his first incarnation who doesn't want to change either.

TARDIS

 * The Master drove his TARDIS too fast towards the black hole and ended up getting stuck on Floor 1056 of the colony ship.
 * The Doctor says that his TARDIS would never be able to properly function because it is too close to the black hole at Floor 0000.

Music

 * The song heard when Missy and the Master are dancing on the rooftop is "Midnight, the Stars and You" by Al Bowlly.

Story notes

 * The read-through for The Doctor Falls took place on 21 February 2017. The final segment of the episode—the Twelfth Doctor with the First Doctor in the snow—was filmed only two weeks before World Enough and Time aired, as part of filming of the Christmas special. Post-production on that scene was completed in the short time left; a week before The Doctor Falls aired, Steven Moffat stated that the final version was still being worked on. The Doctor's near-regeneration outside the TARDIS had to be completed in time for World Enough, a week beforehand.
 * This was the official debut for David Bradley as the First Doctor, after portraying the character in a series of reconstructions for the non-DWU docudrama An Adventure in Space and Time. His first line in the role was: "I will not change. I will not! No, no, no, no. The whole thing's ridiculous."
 * Bradley becomes the fifth actor to play the First Doctor in a televised story following original actor William Hartnell, Richard Hurndall, who played him in TV: The Five Doctors, John Guilor, who voiced him in TV: The Day of the Doctor, and the uncredited child actor who played him in TV: Listen. He also becomes the fourth actor, following Colin Baker, David Tennant and Peter Capaldi, to play the Doctor after having previously played another character in the franchise. In Bradley's case, Solomon in TV: Dinosaurs on a Spaceship, as well as providing the voice of Azure of the Claw Shansheeth for TV: Death of the Doctor on The Sarah Jane Adventures.
 * The Doctor's mention of Marinus as a planet on which the Cybermen originated (COMIC: The World Shapers) is another rare instance of the TV series directly referencing non-televised material.
 * This episode removes any contradiction that had previously revolved around the various Cybermen origin stories, by having the Doctor call all instances parallel evolution.
 * This episode wraps up the stories of several recurring characters;
 * Bill and Heather begin their own travels through time and space, Bill leaving the Doctor behind in the TARDIS.
 * Nardole stays behind on the Mondasian ship to help Hazran and her children escape the Cybermen.
 * is forced to regenerate by Missy after she stabs him. Both agree that he then regenerates into Missy, in his own TARDIS, and he forgets the whole adventure. However, his actual change is not shown on screen.
 * is killed by her previous incarnation, left unable to regenerate. In their own words, they were shot in the back by themselves.
 * The First Doctor states to (unknown to him) his future self: "You may be a doctor, but I am the doctor. The original you might say." This is true in more than one sense and serves as an in-joke: the First Doctor IS the original Doctor.
 * When the Doctor is dreaming of his recent past companions calling him, he sees Clara Oswald. Though fans assume that means his memories of her were back, it was revealed in the next episode that he didn't have them back until the Testimony restored them as a gift.
 * On original broadcast on HD, a technical fault led to sound problems which rendered the dialogue inaudible for the final five minutes: from Bill leaving the TARDIS to the end credits.
 * The use of the number 507 is a nod to Russell T Davies, who often invokes the number 57 in his writings, and who once had the Eleventh Doctor claim to Clyde Langer that he could regenerate 507 times. (TV: Death of the Doctor - the only Eleventh Doctor story written by Davies)
 * A flashback sequence features the Doctor remembering virtually all of his 2005-present companions, including Jack Harkness and Sarah Jane Smith, both of whom appear on screen for the first time in the Steven Moffat era (projected images of Martha Jones, Donna Noble and Rose Tyler had appeared in TV: Let's Kill Hitler, with the Moment taking Rose's form in The Day of the Doctor).
 * Archive footage from two moments in The Pilot are used in the episode.
 * This episode marks the last appearance of Missy's Theme.
 * This is the first multi-Doctor story in which no former actors in the role of the Doctor appear, either reprising their role or through archive footage.
 * This is the first season finale in the revived series and the only episode of Series 10 to feature no scenes on present-day Earth, though the final scene takes place on Earth in 1986.
 * It is unclear whether the Master's "little condition" refers to the Drumming or the instabilities caused by his resurrection in The End of Time, though both are absent in this story.
 * Despite the Master claiming that the blasts from his laser screwdriver killed Missy for good, there is a great deal of doubt among fans that the Master will not return.

Ratings

 * 3.75 million (UK overnight figures)
 * 5.32 million (UK final)

Filming locations

 * Caerwent, Wales - Floor 0507 farmland.

Production errors

 * After Bill blows up the barn, a cameraman is visible on the edge of the shot.
 * In the forest scenes, several pieces of camera equipment are somewhat visible, such as a dolly and a tripod.

Continuity

 * Bill carries the Doctor's unconscious body in much the same manner that the Eleventh Doctor and Rory Williams once carried Amy Pond. (TV: Asylum of the Daleks, The Girl Who Waited) This isn't the first time the Twelfth Doctor has been physically carried in such a manner by a companion, as Clara Oswald also previously carried him this way, though he was not unconscious. (COMIC: Clara Oswald and the School of Death)
 * Companions have previously departed in a Cyberman-related story, notably Adric, Charley Pollard (when parting company with the Eighth Doctor) and Rose Tyler. (TV: Earthshock, Doomsday, AUDIO: The Girl Who Never Was)
 * The expedition to 507 that "Razor" talked about are being used as scarecrows. (TV: World Enough and Time) They, however, walk free at night and attempt to attack the village, but are shot down with rifles. (TV: Human Nature/The Family of Blood)
 * The Master laughs maniacally. (TV: The End of Time)
 * This episode marks the third consecutive time a female has killed the Master. The first was by Chantho (TV: Utopia) and the second was by Lucy Saxon. The Master tended to comment how it was "always the women". (TV: Last of the Time Lords)
 * The clock on the hospital is seen ticking towards one o'clock (or thirteen), away from twelve, shortly before the Doctor is severely injured. Clocks have previously been seen as an indication of the Doctor's impending regeneration. (TV: The Time of the Doctor)
 * The Twelfth Doctor holds out his arms, and waits to be shot, much like his ninth, (TV: The Parting of the Ways) tenth, (TV: Evolution of the Daleks) and eleventh incarnations did. (TV: The Impossible Astronaut, The Wedding of River Song) However, this time he retaliates but destroying all the Cybermen rather than waiting to die.
 * The Master and Missy admit to not knowing how many regenerations the Doctor has left after his regeneration cycle was restored. Both the Doctor and Rassilon previously wondered this. (TV: Kill the Moon, Hell Bent)
 * The Master mocks the Doctor about leaving Bill alone. (TV: World Enough and Time)
 * Missy would later make an entire army of Cybermen from dead humans as her predecessor did. (TV: Death in Heaven)
 * The Doctor recalls last seeing Missy's predecessor heading to Gallifrey, deducing that the Time Lords cured his "little condition" before kicking him out. (TV: The End of Time)
 * The Master gloats over his dominion to a wheelchair bound Doctor just as he did with the aged Tenth Doctor during the Year That Never Was, even calling him "Granddad", (TV: Last of the Time Lords) and to a restrained Doctor upon the rise of the Master Race. (TV: The End of Time)
 * The Doctor notes the Cybermen have risen naturally from Mondas, (AUDIO: Spare Parts, TV: The Tenth Planet) Telos, (PROSE: Doctor Who and the Cybermen) Earth, (TV: Rise of the Cybermen / The Age of Steel) Planet 14 (TV: The Invasion) and Marinus. (COMIC: The World Shapers)
 * The Doctor recounts his various victories over the Cybermen: on Telos where he sealed them into their ice tombs, (TV: The Tomb of the Cybermen) Voga, (TV: Revenge of the Cybermen), Canary Wharf (TV: Army of Ghosts / Doomsday) and Planet 14. (COMIC: The World Shapers, TV: The Invasion) He states: "Every single time, you lose, even on the Moon". (TV: The Moonbase)
 * The Doctor was previously electrically shocked by a Cyberman. (TV: The Pandorica Opens)
 * The Doctor reminds Bill how she remembered the truth during the reign of the Monks. (TV: The Lie of the Land)
 * The Doctor reiterates his dislike of guns, (TV: The Sontaran Stratagem, The Doctor's Daughter, The Impossible Astronaut, The Curse of the Black Spot, Into the Dalek) despite having used them several times, both in general, (TV: Bad Wolf, The End of Time, Flesh and Stone) and with the intent to harm others. (TV: A Town Called Mercy, Dalek, Day of the Daleks, The Invasion of Time, Hell Bent)
 * Nardole reminds Bill that he is still allowed to "kick [her] arse". (TV: Extremis) Bill tells him he will have to go down to the hospital to find it then. (TV: World Enough and Time)
 * Nardole mentions how he used to be a black market dealer before meeting the Doctor, (TV: The Husbands of River Song) and further indicates he is a cyborg. (TV: Oxygen, The Eaters of Light, World Enough and Time)
 * Nardole states that Hazran is "only human", something the Doctor has said numerous times. (TV: The Big Bang, A Good Man Goes to War)
 * Missy is able to provide the Master with a dematerialisation circuit by telling him to always carry a spare, similar to how the Tenth Doctor told the Fifth Doctor how he could stop the TARDIS exploding. (TV: Time Crash)
 * Missy telling her previous incarnation she loved being him also mirrors a sentiment of the Tenth Doctor, as he expressed such to his fifth incarnation. (TV: Time Crash)
 * The Doctor reiterates River's words that Nardole once spoke to him from her diary. (TV: Extremis)
 * Bill is reunited with Heather in the form of sentient oil. She also recalls the moment she asked her to come back for her. (TV: The Pilot)
 * Bill telling the two Masters to stand aside so she can fire at the upcoming Cyberman echoes when the Tenth Doctor told the Master to do likewise when he had a revolver and vice versa as the Master prepared to attack Rassilon. (TV: The End of Time)
 * Missy uses her sonic umbrella. (TV: World Enough and Time)
 * The Master asks the Doctor if he has ever burned to death. Although the Doctor hasn't, the Master has. (TV: Planet of Fire) Missy says that she knows the Doctor has literally fallen to his death as the Fourth Doctor regenerated as a result of falling off the Pharos Project's radio telescope. (TV: Logopolis) The Master asks if the Doctor has ever drowned, which he did while fighting the Racnoss in an alternate timeline. (TV: Turn Left) Missy asks if the Doctor has ever felt the blade, with something similar actually happening to him. (TV: Doctor Who) This last statement foreshadows Missy stabbing the Master with a knife.
 * The Master uses a modified laser screwdriver. (TV: The Sound of Drums/Last of the Time Lords)
 * The Master reveals to Bill that he was Razor and that he hated the 10 years they spent together on floor 1056. (TV: World Enough and Time)
 * The Master once again refuses to listen to the Doctor. (TV: Last of the Time Lords) However, Missy does, in the end, turning back to join him, as she has progressively had a change of heart. (TV: Extremis et al.)
 * Bill chooses the TARDIS as the Doctor's final resting place. In an alternate timeline, the Eleventh Doctor was interred in the TARDIS after his death on Trenzalore. (TV: The Name of the Doctor)
 * The Doctor has a brief recall of some of his past companions from his ninth incarnation onwards, just before his body attempts to regenerate. The Fourth and Fifth Doctor similarly had this occur to him. Like with the Fifth Doctor, the last face he sees is the Master's. (TV: Logopolis, The Caves of Androzani)
 * He recalls Rose Tyler from TV: Bad Wolf, Martha Jones from TV: Daleks in Manhattan, Donna Noble from TV: Partners in Crime, Jack Harkness from TV: Utopia, Vastra from TV: The Name of the Doctor, Jenny Flint from TV: The Crimson Horror, Sarah Jane Smith from TV: The Stolen Earth, Amy Pond from TV: The Impossible Astronaut, River Song from TV: The Pandorica Opens, and even Clara Oswald from TV: Last Christmas, despite having her wiped from his memories in TV: Hell Bent, having previously had some form of recollection in TV: For Tonight We Might Die. He also recalls Missy from TV: The Witch's Familiar.
 * When waking up after his pre-regeneration flashbacks, the Doctor says "Sontarans! Perverting the course of human history!". They were the first words of the Fourth Doctor after regenerating. (TV: Robot) He previously said the same thing after waking up from being knocked out by flying objects due to air pressure. (TV: Listen)
 * As he begins regenerating, the Doctor says "I don't want to go", the same words his tenth incarnation said before regenerating. (TV: The End of Time) He also reiterates the last lines of his eleventh incarnation; "when the Doctor was me"; (TV: The Time of the Doctor) as well saying "it's starting. I'm regenerating", the words the Tenth Doctor stated before his aborted regeneration. (TV: The Stolen Earth) He also shouts "no!" repeatedly while his regenerative energy flairs up, which was what the Second Doctor said as the Time Lords sent him away to exile. (TV: The War Games)
 * The Doctor resists regenerating. He has previously done this when nearing the end of his first, (TV: Twice Upon a Time) fifth, (TV: The Caves of Androzani) ninth, (TV: The Parting of the Ways) and tenth incarnations. (TV: The End of Time)
 * The Doctor offers people jelly babies. (TV: The Three Doctors, Robot, et al.)
 * The Master refers to the Doctor as "Doc". The Doctor's first incarnation had previously taken umbrage at being addressed like that, (TV: The Time Meddler, The Five Doctors) as did his sixth (TV: The Twin Dilemma, The Ultimate Foe) and tenth. (TV: Dreamland)
 * It is revealed that Heather gave her tears to track Bill, explaining how Bill was still able to cry despite being a Cyberman. (TV: World Enough and Time)
 * The cyber-converted Yvonne Hartman, who had managed to retain her free will after conversion, also displayed the ability to cry; however, she cried oil rather than actual tears like Bill. (TV: Doomsday)
 * The Doctor meets his first incarnation. He has met this version of himself on numerous previous occasions. (TV: The Three Doctors, The Five Doctors, The Day of the Doctor, PROSE: The Eight Doctors)
 * The Doctor and Bill both recite the line "where there's tears, there's hope" at different points. A similar line, "while there's life, there's hope," served as the final words of the Third Doctor, while trying to console a crying Sarah Jane Smith. (TV: Planet of the Spiders) Ben Jackson said the same thing during the events on Snowcap. (TV: The Tenth Planet)
 * As the Doctor leaves the TARDIS the cloister bell is heard ringing. (TV: Logopolis et al.)
 * The Twelfth Doctor, and later the First Doctor, describe themselves as "the Doctor, the original you might say." The First Doctor previously said this exact phrase to Tegan Jovanka. (TV: The Five Doctors).
 * Missy severely injures one of her previous incarnations. The Master previously played a part in one of his own past regenerations due to the manipulations of the Cult of the Heretic. (AUDIO: The Two Masters)
 * Bill was strong enough to survive the cyber-conversion process while retaining her humanity, largely in part due to the strong attachment she had to her deceased mother. (TV: The Pilot et al.)
 * Yvonne Hartman and Mercy Hartigan were also able to retain their consciousness following their conversions. (TV: Doomsday, The Next Doctor)
 * The Doctor had previously encountered a version of Clara Oswald who had been strong enough to survive a Dalek conversion process and retain her humanity, she too had few memories of the conversion and believed she was still human. (TV: Asylum of the Daleks)
 * Craig Owens had previously been able to resist a Cyber-conversion due to his strong love for his son overpowering a damaged cyber-ship's conversion equipment. (TV: Closing Time)
 * The Master being stranded by a malfunction, or by his TARDIS otherwise being unavailable to him has happened to him several times. (TV: The Claws of Axos et al., AUDIO: Sympathy for the Devil et al.)
 * The Doctor comments that it's a pity there are no stars in view when he seemingly dies, echoing an affection voiced earlier in his life: "the deep, lovely dark; you'd never see the stars without it." (TV: Listen)
 * The Masters discuss how an earlier incarnation cannot clearly remember what they learn from meeting a future one. (TV: The Day of the Doctor)
 * Heather mentions Bill's job of serving chips at St Luke's University. (TV: The Pilot, World Enough and Time)
 * The Doctor faces Mondasian Cybermen that can fire energy beams from their headframe. He already did so during his eighth incarnation. (COMIC: The Flood)
 * Missy (seemingly) dies in a field of white flowers - her first appearance had her dancing around a field of white flowers. (TV: Deep Breath)
 * The Doctor and Bill part ways, unknowing of each others fates. The Doctor and Clara previously departed on somewhat similar terms, having believed each other's lies about a happy ending. (TV: Death in Heaven)
 * This is the second time that Mondasian Cybermen cause the Doctor to regenerate. (TV: The Tenth Planet) Interestingly, the Twelfth Doctor ends up meeting the incarnation from said event after their encounter with the Cybermen. (TV: Twice Upon a Time)

DVD releases
This episode was released as part of the Series 10 DVD box set on 13 November 2017.

Blu-ray releases
to be added

Digital releases
to be added