Hell Bent (TV story)

 was the twelfth episode of the ninth series of Doctor Who produced by BBC Wales and is the second half of its two-part finale.

It was the final regular appearance of Jenna Coleman as Clara Oswald. Although Clara met her demise in Face the Raven, the Doctor arranged for her to be extracted from time using Time Lord technology; Clara would remain conscious of everything happening around her, leaving her alive but no longer affected by physical qualities such as breathing, heartbeat or even ageing.

It featured the return of the Time Lords, who last featured (albeit only off-screen) in The Time of the Doctor. Among them was Rassilon, now in a new incarnation after his previous body was last seen being attacked by in The End of Time. Rassilon was banished from Gallifrey, along with the High Council, after losing the allegiance of his race for his cruelty to the Doctor and his role as one of the driving forces of the Last Great Time War. He was also deposed as Lord President, with the Doctor briefly assuming it in his place. Also returning was the General, who regenerated and was revealed to be a usually-female Time Lady who had assumed a male incarnation, marking the first instance of an on-screen regeneration where a Time Lord changed genders, as well as being a rare on-screen instance of a Time Lord also changing skin colour.

Ohila and the Sisterhood of Karn also reappeared, wherein Ohila was hinted to have a greater personal history with the Doctor that may have gone back to his earlier days. Ashildr made another appearance as well, having persisted to the final moments of time. She eventually ended up in possession of a TARDIS which the Doctor stole, and began travelling with Clara, who was not ready to return to Gallifrey and face her end.

Hell Bent ended up being full circle for both the Doctor and Clara. For the Doctor, he was once again running away in his TARDIS. For Clara, she was now time-travelling again, aboard a stolen TARDIS with an original control room layout similar to the one which the First Doctor stole, with Ashildr, another long-lived being, as her companion. They were unable to get the chameleon circuit on this TARDIS working properly, leaving its exterior stuck in the form of an American diner which the Doctor had visited in The Impossible Astronaut. The story also saw the return of the sonic screwdriver, a brand new model to replace the Sonic Screwdriver seen since its debut in 2010.

This story depicted the Doctor reaching his limit, seeing him break his own moral codes, step away from being the Doctor and unleash his fury on the Time Lords in an attempt to save his companion's life, which came with the price of losing his memories of Clara as atonement for what he had done. Additionally, several facts about his past before fleeing Gallifrey and prophecies of the Hybrid were revealed, though who or what the Hybrid was remained uncertain.

Synopsis
After being tortured for billions of years within his own confession dial, the Doctor has been pushed to the brink of madness. Returning to Gallifrey, he must face his own people, the Time Lords, but how far will he go in his quest for vengeance? Does he have another confession? And how fiercely does his rage towards them for causing Clara's death burn?

Plot
In the Nevada desert, the Doctor walks into a diner, and is greeted by a waitress who looks and sounds exactly like Clara Oswald. Having no money, he tells her he can play his guitar. As he starts to play her a song, she asks him if it is a sad song. He says that nothing is sad until it's over. He tells her that he thinks the song is called "Clara". The waitress asks him to tell her about this "Clara"...

Walking through the desert-like plains of Gallifrey, the Doctor arrives at the old barn where he slept in as a child and worked out how to save his home. He climbs up into its loft, seeming nostalgic as he overlooks his old bed. A woman he recognises enters the barn; with the Doctor's face blocked by a beam, she cannot tell who it is, so she asks him to leave. Walking closer, she meets his gaze, immediately realizing his identity; she warns the Doctor that "they" will kill him. In the chamber of the High Council, the Cloister Bells are ringing, warning of great danger. Rassilon wonders why the Doctor hasn't arrived yet. To Rassilon's annoyance, Ohila and some of the Sisterhood of Karn arrive uninvited and advise to try appealing to the Doctor to get his attention; he doesn't blame the Time Lords for the horrors of the Time War, just Rassilon. Rassilon sends a soldier named Gastron to retrieve him.

In the meantime, the Doctor is trying to enjoy a bowl of soup, with a small crowd of Gallifreyans watching him in awe. Gastron arrives in a military craft, asking that the Doctor drop his weapons. Instead of going with Gastron, the Doctor walks up and drags his heel through the sand, drawing a line; he then resumes eating his meal, unconcerned. Gastron reports this to Rassilon, who tries numerous different approaches to get the Doctor's attention - he sends the General and respectful soldiers, and even the High Council.

Finally, Rassilon himself arrives with his personal guard; the Doctor only responds with a simple "Get off my planet". Rassilon does not take kindly to the Doctor's words, demanding he come with them. However, the Doctor still refuses to comply, forcing Rassilon to order his execution; he threatens them into complying by raising his Gauntlet. To Rassilon's anger and surprise, they all miss; he demands an explanation from Gastron. He states that in the Time War, the first thing that was noticed about the "Doctor of War" was that he was unarmed, and that "For many it was also the last." Gastron throws his weapon and joins the Doctor. The rest of the firing squad follow suit.

Raising his Gauntlet, Rassilon demands to know how many regenerations were granted to the Doctor back on Trenzalore; he intends to keep killing the Doctor until he runs out of regenerations. However, to Rassilon's surprise, reinforcements arrive, backing up the Doctor. The General repeats the Doctor's order to leave the planet, throws down his gun and joins the Doctor. Rassilon is then banished, with the Doctor stating that the High Council that served him will soon be following. The General then explains that Gallifrey came back into the universe several billion years later, give or take a star system or two; thus anyone banished from the planet has little choice in where to go. The General asks if he's gone too far with Rassilon's exile, the Doctor grimly warns that he's barely started.

Now once more the Lord President of Gallifrey, the Doctor demands to know why he was imprisoned within his own confession dial. The General explains that all Matrix predictions foresaw the birth of a Hybrid of both Time Lord and Dalek races. The Doctor explains that Time Lords always jump to conclusions; the Daleks would never allow anything to be half-Dalek, because of their insane idea of racial purity. However, he then refuses to explain further as he needs Clara to talk to, implying she knows of the Hybrid. They take him to the extraction room, where they pull Clara out of her timeline one second right before her death; she arrives on Gallifrey, confused.

The Doctor explains that she's been frozen in that one moment of time they took her from, so that she doesn't have a pulse or need to breathe (though she still does so out of habit). Once the General explains why they saved her, the Doctor reveals it was all a ruse to save Clara and disarms the General. After asking what regeneration the General is on (his tenth), the Doctor wishes him luck before shooting him with his own gun. As the Doctor and Clara flee, Gastron checks on the General, who has regenerated into a female; she is quite glad to have returned to her original gender, which is free of male ego.

The Doctor takes Clara to the Cloisters, an area located below Gallifrey's capital; it is guarded by Wraiths, which only attack if they attempt to leave. Many enemies attempted to steal information from Gallifrey during the Cloister Wars, and were imprisoned within the vines. There is a secret door they can use to escape, he used in during his childhood when he got lost; the wraiths use projections of enemies who attacked to attempt scaring them into retreating, to no avail. The General and Ohila arrive via the elevator, but don't stray more than three feet from it as any further in would cause the Wraiths to attack them as well. Clara, meanwhile, discovers that the Doctor does not know what the hybrid is and was only using his apparent knowledge in a gambit to get to Gallifrey and use their technology to save her from death.

Concerned the Doctor refuses to reveal how long he was in the confession dial, she asks Ohila and learns he refused to answer about the Hybrid for 4 1/2 billion years (the Doctor could have left if he answered), shocking Clara that he had gone so far just for her. Turning to the Doctor, she tells him at "people like me and you, we should say things to one another" and proceeds to do so - words kept private from the audience and from the General and Ohila, to whom she refuses to divulge what she said. Instead, she distracts the General and Ohila with a furious tirade - "Do you know why you hide here at the end of time? You're monsters! You are hated. You. Are. Hated. And by no-one more than me." (Clara's hatred is for what they did to the Doctor and her, all just to get some answer.) The Doctor escapes through a secret tunnel; he proceeds to steal another TARDIS and flees Gallifrey with Clara. Ohila isn't that surprised; she explains to the General that running away is what the Doctor does best.

Inside the TARDIS, the Doctor asks Clara what she thinks of the original design for the control rooms; she's not too fond of it. The Doctor takes them to Gallifrey's remains at the end of the universe, hoping that Clara's biology will restart now that there's nothing that can be damaged by his actions. However, the Chronolock is still on the back of Clara's neck; he's failed to save her, again, and begins ranting to her about no longer being accountable to anyone. Hearing four knocks, the Doctor tells Clara that Me is out there; he leaves the TARDIS to find Me sitting in a chair next to a fireplace. The Doctor reminds Me that he told her the universe would be small when he's angry at her; he tells her to "go to Hell, which is about five minutes away." Me explains that she's managed to stay alive by creating a reality around the Cloisters on Gallifrey; she's the last thing in the universe, having finally earned the title Me.

Me then asks about the Hybrid, which the Doctor thought was her, human with Mire medical technology inside; Me speculates it might refer to the Doctor and theorizes that the Doctor might be half-human. However, the Doctor brushes her off, asking if it matters. Following this, Me wonders if it's the relationship between the Doctor and Missy - order and chaos side by side, traveling the universe; the Doctor finds the idea more believable. Me then reveals her true theory: she thinks it's the Doctor and Clara - true companions who will go to extremes for the sake of each other. The Doctor informs Me of the device which will wipe Clara's memories of him, but promises to tell her before he does it.

Clara watches on the monitor, coming to learn that the Doctor plans to erase all memory of himself from her, then drop her off somewhere to live her life. When the Doctor and Me enter the TARDIS, Clara argues with him, demanding to keep her memories and revealing that she had used the sonic sunglasses to "reverse the polarity" of the neuroblock device to erase the Doctor's memory if he used it on her. The Doctor is skeptical that she could do this, however, they both agree to take a fifty-fifty chance to have one of their memories wiped at random. After Clara suggests they forget the whole thing and just "fly away somewhere", they both touch the device, and press the button. It turns out the Doctor is the one to lose his memories. He collapses in pain to the floor. Before losing his memories, he gives out advice, from "never be cruel or cowardly", to the more bizarre "never eat pears". He asks Clara for one last smile before he blacks out.

Back in the present, the Doctor continues talking to Clara; he doesn't remember what she looked like, or the "very important" message she gave him in the cloisters, but remembers their adventures and half-heartedly says he is trying to look for her. Clara tries one last time to spark a memory by outright suggesting that she could be Clara, only to have the Doctor assert that he would "absolutely know" if he ever saw her again, causing Clara to turn away to hide her tears. Looking around the diner, he suddenly recalls having been to it with River, Amy and Rory when he faked his death in his previous incarnation. He tells Clara that he is currently searching for his own TARDIS, as it has disappeared from where he left it in London. As he begins once again to play the sad melody he'd been playing, Clara smiles and reminds the Doctor what he told her about that memories become stories; while he can't remember what she told him in the cloisters, she suggests sometimes lost memories become songs. The Doctor compliments the sentiment and momentarily turns his back, as Clara walks into the back room, which is revealed to the console room for the TARDIS they stole from Gallifrey. The diner vanishes, leaving the Doctor astounded as he realizes he was talking to Clara; he then turns around to find his TARDIS, which still has Rigsy's graffiti memorial for her, left behind.

In Clara's TARDIS, Me tells her the Chameleon circuit is broken, but she is unconcerned, saying that she likes it. Clara asks Me whether the Time Lords can return her to her place and time of death, knowing she will have to face the raven eventually, to which Me responds with the affirmative. Me asks Clara where will she go now, she replies "Gallifrey, the long way around": she isn't going back to face her death just yet.

The Doctor boards his long-abandoned TARDIS and takes off, watching a new sonic screwdriver emerge from the console and launch into the air and catching it. He then sees Clara left a message for him on the blackboard - "Run you clever boy, and be a Doctor." As the TARDIS dematerialises the memorial on the front door flakes off piece by piece-any trace of Clara having been with the Doctor now gone.

The Doctor's TARDIS is shown traveling through space, the Doctor once again setting off on a brand new adventures - unaware that Clara and Me's TARDIS quickly passes by his, setting off their own journeys through space and time.

Cast

 * The Doctor - Peter Capaldi
 * Clara - Jenna Coleman
 * Ashildr - Maisie Williams
 * The President - Donald Sumpter
 * The General - Ken Bones
 * Female General - T'Nia Miller
 * Gastron - Malachi Kirby
 * Ohila - Clare Higgins
 * The Woman - Linda Broughton
 * Man - Martin T. Sherman
 * Wraiths - Jami Reid-Quarrell, Nick Ash, Ross Mullan
 * Voice of the Dalek - Nicholas Briggs

Story notes

 * Although the episode is officially considered the second part of the story begun in TV: Heaven Sent, narratively it is the third chapter of a trilogy that begins with TV: Face the Raven.
 * This is the first Doctor Who television story to actually show a regeneration from a male body to a female. There have been references to this having happened with the Corsair (The Doctor's Wife) and the Master (Dark Water, Death in Heaven), and it was one of the options the Eighth Doctor received in The Night of the Doctor, but it has never been featured on a televised story until now, in this case the General from his eleventh to twelfth incarnation.
 * It also shows the first change of skin colour from white to black. The first incident was of Melody Pond to Mels, but the change was never seen, but the change the other way around was seen in TV: Let's Kill Hitler.
 * This marks the first time a Doctor Who television episode has had the minor expletive "hell" in the title. The word previously appeared in the titles of the comic stories A Cold Day in Hell! and The Road to Hell as well as the audio story Minuet in Hell.
 * This episode marks the first televised appearance of an interior shot of a TARDIS other than the Doctor's since Time and the Rani, the latter being the Rani's. It is only the second TARDIS control console seen other than the Doctor's since Time and the Rani, after the Junk TARDIS in The Doctor's Wife.
 * The tune played by the Doctor when he was sitting in the diner is a simplified version of Clara Oswald's theme from the Series 7-9 soundtracks. It is a rare example of a piece of incidental music composed for Doctor Who becoming part of its in-universe narrative. The Doctor says he believes the song is called "Clara". "Clara?" is the name of the track on the Series 7 soundtrack, though it has also been performed at the Proms and other events as "The Impossible Girl" and was titled "Clara and the TARDIS" on the soundtrack for The Snowmen, which featured the first appearance of the melody. In the context of the story, it is implied that the melody represents the now-forgotten words Clara says to the Doctor in the Cloisters; this is supported by the fact the same piece of music plays (in a full orchestral version) when the episode cuts away from the couple as Clara begins to speak.
 * The Radio Times programme listing was accompanied by a small colour head-and-shoulders shot of the General, with the accompanying caption "Doctor Who / 8.00 p.m. The General (Ken Bones) prepares for battle in the series finale".
 * Although they only receive a brief cameo, the inclusion of the Cybermen ensures the continuation of a pattern that has been ongoing since Series 5, whereby they appear in every twelfth episode of a series.
 * This story marked the first mention of the Web of Time in the revived series.

Ratings

 * BBC One Overnight: 4.8 million
 * BBC America Overnight: to be added
 * Final UK ratings: 6.17 million

Myths

 * The Twelfth Doctor's appearance in TV: The Day of the Doctor would be accounted for. This was something that was hinted at during production and early publicity for Series 9 - including public statements made by Capaldi. Ultimately, however, while the episode in itself was a sequel to Day of the Doctor'', no reference is made to the Twelfth Doctor's appearance during the battle and the story affords no opportunity for this event to occur.
 * The diner waitress would be an echo/splinter of Clara Oswald. False. This rumour originated when images of Jenna Coleman in a waitress uniform appeared in media including Doctor Who Magazine prior to broadcast of Hell Bent, with no corresponding scene having occurred before Clara's death in Face the Raven.

Filming location
to be added

Production errors

 * When taking off in the getaway TARDIS, Clara's hair changes from combed, to messy, to combed again, in a series of jump cuts. Similarly, her hair is noticeably different at the moment time freezes on the trap street than in the flashback footage from Face the Raven.
 * The chronolock tattoo is not visible on Clara in the diner or final TARDIS scenes. (According to a December 2015 Twitter posting by director Rachel Talalay, this was intentional but she did not elaborate.)

Continuity

 * Rassilon and the High Council reappears.(TV: The Five Doctors, The End of Time, et al)
 * A Dalek invasion of the Matrix had previously occurred. (AUDIO: Ascension)
 * Before the Doctor shoots the General, he asks "Regeneration?", to which he replies "Tenth", reminiscent of an exchange between the First Doctor and the Fifth Doctor in the Death Zone. (TV: The Five Doctors)
 * The Doctor mentions a 20 foot wall harder than diamond, Ohila says how long the Doctor spent trapped, and the General says he could have just said what he knew. (TV: Heaven Sent)
 * The Doctor mentions the Academy. (TV: The Deadly Assassin et al)
 * The Doctor mentions the time he was the First Doctor. (TV: An Unearthly Child et al)
 * The Doctor mentions his "duty of care". (TV: Under the Lake)
 * The Doctor mocks the Time Lords' dress sense. (TV: Time Crash, Journey to the Centre of the TARDIS et al)
 * Charlotte Pollard had previously wiped the Sixth Doctor's memory so that he forgot travelling with him and went on other adventures afterwards with in her case the Viyrans. (AUDIO: Blue Forgotten Planet)
 * The Doctor enters the Repair shop. (TV: The Name of the Doctor)
 * The Doctor steals a TARDIS and runs away. (TV: The Name of the Doctor)
 * The Web of Time is mentioned. (AUDIO: Neverland et al, TV: The Two Doctors et al)
 * The Chronolock still appears on Clara's neck. (TV: Face the Raven)
 * The TARDIS' classic sound when the doors opens can be heard. (TV: An Unearthly Child et al)
 * The General said that Rassilon was once a good man. (TV: The Five Doctors)
 * The Doctor mentions his warning to Me on the trap street. They talk about the circumstances around Clara's death as well. (TV: Face the Raven)
 * The Doctor's TARDIS provides him with a new sonic screwdriver. (TV: The Eleventh Hour, et al)
 * Clara and Ashildr are unable to get their TARDIS' chameleon circuit to function properly, like the Doctor himself, leaving its outer shell stuck in the shape of an American diner that the Doctor recalls visiting with Amy Pond, Rory Williams and River Song, (TV: The Impossible Astronaut) mirroring the Doctor's own issue with his own. (TV: An Unearthly Child, et al) Similarly, Clara claims to not mind, just as the Doctor himself has previously explained. (TV: Rose, et al)
 * Prior to dematerialising, the Doctor's TARDIS still has Rigsy's Clara Oswald memorial graffiti on it. (TV: Face the Raven) However, the graffiti is removed before the TARDIS moves on; unlike in TV: World War Three, however, the TARDIS removes it herself. The TARDIS previously removed posters plastered all over it when travelling through the time vortex. (TV: Vincent and the Doctor)
 * When the Doctor first walks into the diner, the song Don't Stop Me Now as performed on the Orient Express can be heard in the background, apparently playing on a jukebox. (TV: Mummy on the Orient Express)
 * The Doctor again plays his guitar. (TV: The Magician's Apprentice, Before the Flood)
 * The Doctor returns to the barn where he nearly detonated the Moment, (TV: The Day of the Doctor) and briefly lies on the bed where Clara spoke to his first incarnation in a "dream" during his childhood. (TV: Listen)
 * The Doctor extracts Clara from her death point on the trap street. (TV: Face the Raven)
 * The Doctor, when threatening with shooting the General and the extractors, mentions selfies. (TV: The Woman Who Lived)
 * Clara mention that the Doctor said Gallifrey was frozen in another dimension. (TV: The Day of the Doctor, The Time of the Doctor, Death in Heaven) The Doctor says that it had somehow become unfrozen. (TV: The Witch's Familiar)
 * A baby-Weeping Angel could be seen in a corner in the Cloisters. (TV: The Angels Take Manhattan)
 * Weeping Angels can be seen in the Cloisters. (TV: Blink et al)
 * Cybermen can be seen in the Cloisters. (TV: The Tenth Planet et al)
 * A Dalek can be seen in the Cloisters. (TV: The Daleks et al)
 * A Mire helmet can be seen in the Cloisters. (TV: The Girl Who Died, The Zygon Inversion)
 * The Doctor still has his confession dial. (TV: The Magician's Apprentice, The Witch's Familiar, Face the Raven, Heaven Sent)
 * The reality bubble that Ashildr/Me uses to watch the universe die encloses a ruined section of the Cloisters from Gallifrey. The Doctor previously stated that Me was the Hybrid destined to stand in the ruins of Gallifrey. (TV: Heaven Sent)
 * The Doctor states that he returned to Gallifrey "the long way around", while Clara also states that she plans to return to Gallifrey in the same manner. (TV: The Day of the Doctor, Heaven Sent)
 * The Doctor finds himself once more at the end of the universe. (TV: Utopia, Forest of the Dead, Listen, PROSE: The End, Midnight in the Café of the Black Madonna, Do You Love Anyone Enough?, Engines of War)
 * When threatening to kill the Doctor, Rassilon inquires into the number of regenerations granted to the Doctor as part of his new cycle, but no answer is given. (TV: The Time of the Doctor) The Doctor himself claimed to be uncertain as to the answer to this question, as he has previously speculated that he may be able to regenerate indefinitely. (TV: Kill the Moon)
 * The Doctor refers to the Cloister Wars and the night he apparently stole the moon and the President's wife, (TV: The Magician's Apprentice) although he credits the latter as being a rumour spread by the Shobogans. (TV: The Deadly Assassin) Clara instantly recognizes these tales due to Missy having told her. (TV: The Magician's Apprentice)
 * A Time Lord soldier refers to the "Doctor of War", while the General refers to the Doctor as the man who won the Time War. (TV: The Day of the Doctor)
 * When Gastron tells the Doctor to drop all weapons, the Doctor drops his spoon. The Doctor once successfully duelled a sword-wielding Robin Hood with a spoon. (TV: Robot of Sherwood)
 * The General changes gender (PROSE: Interference - Book One, Interference - Book Two, Harvest of Time, TV: Deep Breath, The Doctor's Wife) and skin tone (TV: Planet of the Spiders, Let's Kill Hitler, Death of the Doctor) as a result of his regeneration.
 * The Doctor assumes the title of Lord President of Gallifrey once more. (TV: The Invasion of Time, The Five Doctors) As with his fifth incarnation, he vacates the position by running away from Gallifrey. (TV: The Five Doctors)
 * The Doctor's promise that he made to himself "Never cruel or cowardly" is alluded to by Ohila, who asks if the Doctor was being cruel or cowardly toward Rassilon, and by the Doctor himself to Clara just before he passes out. (TV: The Day of the Doctor)
 * The Doctor closes the TARDIS doors with a snap of his fingers once more. (TV: Forest of the Dead, The Eleventh Hour, Day of the Moon, et al)
 * Clara's affinity for TARDIS controls is yet again demonstrated, (TV: Listen, The Woman Who Lived et al) being able to fly her TARDIS without guidance from the Doctor like she had previously required or a TARDIS Instruction Manual like Ashildr. This mirrors the Doctor's first question to her after his regeneration (TV: The Time of the Doctor)
 * The Doctor implies that he was referring to Ashildr when he stated that the Hybrid was "Me". (TV: Heaven Sent)
 * Ashildr theorises that the Doctor could be the Hybrid, suggesting that he is half Time Lord and half human. (TV: Doctor Who)
 * The Doctor once more displays his ability to defeat enemies by standing his ground and not resorting to force. River Song once mentioned that "her Doctor" could do things like this when talking about him. (TV: Forest of the Dead)
 * Clara and Ashildr's TARDIS has a similar console room design to the Doctor's TARDIS during his early travels with it (TV: An Unearthly Child), and its original exterior is the same as the original exterior of the Doctor's TARDIS when he first stole it. (TV: The Name of the Doctor)
 * The Doctor recalls an encounter with an Ice Warrior on a submarine (TV: Cold War) and seeing a Mummy on the Orient Express (TV: Mummy on the Orient Express) while travelling with Clara.
 * Preparing to wipe Clara's memory of him with a neural block, the Doctor notes that he has done this before using telepathy. The Tenth Doctor previously wiped Donna Noble's memory of him to prevent her mind from burning up after she was given his Time Lord knowledge after interacting with the Meta-Crisis Tenth Doctor. (TV: Journey's End) The Time Lords also previously wiped his companions Jamie and Zoe's memories of the Doctor aside from their first adventure with him after passing judgement at his first trial. (TV: The War Games)
 * When there is a knock on the TARDIS door, the Doctor mentions that it is "always four knocks". (TV: The End of Time)
 * Ashildr refers to the Doctor's dislike of endings. (TV: The Angels Take Manhattan)
 * Both the Doctor (TV: The Magician's Apprentice, et al) and Clara (TV: The Girl Who Died, Face the Raven) use the sonic sunglasses.
 * Clara leaves a message for the Doctor on his blackboard. (TV: Listen, et al)
 * The message Clara left is similar to one used by herself and her various splinters. (TV: Asylum of the Daleks, et al)
 * Clara says she reversed the polarity of the neural block, mirroring a phrase the Doctor has used on numerous occasions dating back to the days of his third incarnation. (TV: The Sea Devils, The Day of the Doctor et al.)
 * Clara once again objects to having her memories wiped (TV: Face the Raven, Journey to the Centre of the TARDIS, COMIC: Four Doctors). This isn't the first time the Doctor has considered doing so without her consent. (TV: The Snowmen) She also willingly allowed the Doctor to erase some of her memories on at least two prior occasions (TV: Time Heist, Before the Flood).
 * Important information about a friend is forgotten. (In TV: Journey to the Centre of the TARDIS, Clara learns the Doctor's name but loses the memory.)
 * Clara now knows the exact time and place of her death, something she previously indicated she did not want to know in advance. (TV: Deep Breath, Listen)
 * 's bringing the Doctor and Clara together is mentioned. (TV: The Bells of Saint John, Deep Breath, Death in Heaven)
 * Ashildr states that the Master loves chaos. (TV: Terror of the Autons, et. al.)
 * Hybrids are mentioned again. (TV: The Witch's Familiar et al)
 * The Doctor mentions his hate of pears. (Previously mentioned in a video the Doctor records for Martha in TV: Human Nature; in the episode, the video is seen playing in fast-forward. What the Doctor says is revealed, alongside some real-life ad-libbing by David Tennant, in a slowed-down version of the video included as a DVD bonus feature.)
 * The Hybrid prophecy is mentioned again, with multiple possibilities cited. (TV: The Witch's Familiar, Heaven Sent)
 * Once again the Doctor, when faced with the loss of Clara and breaking the rules to save her, asks an old acquaintance whether, after all he's done for the universe, doesn't it owe him this? (TV: The Snowmen)
 * The Doctor finds himself asking the question: "Clara Who?" (TV: The Snowmen)
 * The Doctor again attempts to change history in order to save Clara (TV: Before the Flood), except on a potentially wider scale.
 * Clara invites the Doctor to fly away with her, paralleling his invitation to her when reconnecting at Christmas. (TV: Last Christmas)
 * Clara notes she is no longer aging; the restoration of her youth was important to her after waking from a dream where she was very old(TV: Last Christmas). Jack Harkness previously discussed how immortality affected his aging (TV: Last of the Time Lords).
 * The melody, "Clara", that the Doctor finds himself obsessively playing on his guitar becomes, for him, a form of earworm (TV: Under the Lake).

DVD releases
to be added

Blu-ray releases
to be added