Listen (TV story)

 was the fourth episode of the eighth series of Doctor Who produced by BBC Wales. It explored a theory proposed by the Doctor due to past experiences, leading to some exploration of his childhood; as such, it gave viewers their first view of the Doctor as a child. This episode also marked the first non-archival appearance of the First Doctor on television since The Five Doctors in 1983, with glimpses of him as a young boy. It is also one of few Doctor Who episodes to not feature an antagonist in any form.

Synopsis
The Doctor has been pondering a question: have people ever been truly alone? Does something lurk unseen beside us all? With Clara at his side, the Time Lord will find himself delving into familiar pasts and eerie futures. Just where does the answer to the old man's unanswerable question lie? Will he find the answers he's been searching for, or will his quest cost him his life this time?

Plot
The Twelfth Doctor is meditating on top of his TARDIS as it hovers above Earth when suddenly he cries out "Listen." Talking to himself, he postulates why people talk out loud when they are alone. He hypothesises that it is because people inherently know that they are not alone. He uses his blackboard to mark down that evolution produces survival skills. He notes that there are perfect hunters and perfect defences, but wonders why there is no such creature that is perfect at hiding. Placing down the chalk he ponders that if evolution created a creature whose purpose was to hide, how would you know, detect, or sense it? Concerned, he asks out loud what the creature would want and what it would do; emphatically crying out to the dark "What would you do?" He chuckles and turns around to see that the chalk he was using is gone, and it then falls to his feet. Looking at the chalkboard, he sees the word “LISTEN”... Clara Oswald is returning home from her date with Danny Pink, obviously distraught. Through flashbacks, it is seen that the dinner date has gone badly wrong. Danny becomes hostile when Clara makes a joke about him knowing about killing another person, and points out that he has done things that have helped others. Clara apologises throughout. He apologises and explains that people like her get the worst of it. She grows defensive and insists that he is making presumptions about what "she" is like. Through the growing miscommunications, she storms out of the restaurant and Danny slams his head against the table after she leaves.

Back at her apartment, she is at home drinking tea before going to her bedroom. She finds the Doctor has parked his TARDIS inside her bedroom. She asks why he has done this and he says he thought it best to hide since she had a date. He notices that she is home early and asks if it went wrong, or if this is good by her standards. She admits that it turned out horribly and that she is upset. Disregarding her mood, the Doctor insists he needs her for "a thing". She says that she cannot but he argues that she is free. She replies by stating that it is possible that she will soon get a phone call, hoping that Danny will call her. He tells her that it is too late for that, as she has already taken off her makeup. Though she argues that she has not, he ignores her and goes into the TARDIS.

While inside, the Doctor tells her his hypothesis about the possibility of a silent entity that always hides. Concerned, she asks the Doctor how long he has been travelling alone, to which he responds, "Perhaps I never have." Clara studies the word written on the chalkboard, noting that it looks like his handwriting. He says that it is not possible that he wrote it and just forgot, to which she laughs and asks "Have you met you?" Her attention wanders over towards a bunch of books and notes on a nearby desk. The Doctor explains that he has been studying people's dreams, and postulates that everyone has at some point in their lives had the same dream. In this dream, they wake up in their bedroom but feel as though someone else is there in the dark. While the dreamer tries to convince themselves that they must be alone, they are unable to shake the feeling that there is something in the room. And just when they almost, for one second even, successfully convince themselves that they're alone, they feel a hand grab their ankle from under the bed. The Doctor says that he has a very obvious question to which Clara quickly responds by asking "Have you had that dream?" The two banter over who asked the question and who should respond first, before Clara gives in and admits that she probably had that nightmare at one point in her life.

The Doctor connects her to the TARDIS telepathic circuits and asks that she concentrates on the time she had the dream. He explains to not break concentration and to remember when it was and how it felt, so that the TARDIS can lock onto the correct date and location. While she is focusing, her mobile phone begins to ring. Her mind wanders towards Danny and him waving when she arrived at the restaurant earlier. The Doctor insists that she not break her concentration and throws her phone aside.

The TARDIS lands and the Doctor is positive that they made it to the correct time and place. Clara is unsure as she admits that she got distracted. He states that the date, the mid-90s, is fine and they step outside to the West Country Children's Home in Gloucester. Clara states that she has never been to Gloucester in her life nor has she ever lived in a children's home. The Doctor ignores it saying that she has likely simply forgotten. When Clara asks if it would be bad to encounter her former self, the Doctor admits that it is potentially catastrophic, and tells her to wait inside the TARDIS while he investigates.

As he goes inside, Clara notices a boy inside staring out of a window. He waves at her very similarly to the way that Danny did earlier. The boy opens the window and they begin talking. Clara asks the boy what his name is. He replies that his name is Rupert, and she seems relieved until he says that his surname is Pink. He thinks it is a stupid name. When she says that it is not and that she knows someone else who shares the same last name, he corrects her and explains that he dislikes his first name and intends on changing it.

Meanwhile, the Doctor encounters the night manager. The Doctor uses his psychic paper to play himself off as an inspector, which comes across as odd as it is 2:00 a.m. The Doctor asks the manager if he finds himself talking out loud to himself, to which he admits to and explains that it is in connection with the children's home. The Doctor asks if he ever notices placing down his coffee mug for a moment only to have it move to another location, which the manager insists happens to everyone. While they are conversing, Clara silently walks up the stairs behind them. The television shuts off and the manager turns towards it exclaiming that it does that habitually. When he turns around, the Doctor is gone and when he looks down his mug has disappeared. The Doctor walks down the hall with the missing mug, taking a sip of coffee before continuing onwards. Clara enters Rupert's room where she finds him sitting on the floor propped up against a bookcase. Sitting on his chair she points out that he should have more chairs for when there are visitors. Rupert points out that they can sit on the bed and she asks why he is not in bed himself. He admits that he believes there is something under the bed. She asks if he had a dream where someone reaches out and grabs him from underneath the bed. He admits that he had the dream and asks how she knows. She avoids the question by pointing out that dreams are simply dreams and are not real. To prove it she goes underneath his bed and has him follow her, insisting that it is harmless. Rupert says that sometimes he hears noises, but she says that it could be other people inside the home and that the noises are nothing to be afraid of.

Suddenly, someone sits on the bed and the mattress presses down. She asks Rupert if there is anyone else in the room, to which he says that there is not. She says that someone must have come in, but he says that no-one has. Clara emerges out from under the bed to find someone sitting on the bed shrouded in the cover. She tries talking to the person but it does not respond. She asks Rupert if it is a friend playing a game but he shakes his head. She asks the person if they are playing a trick on Rupert to which the person stands up. Clara insists that it is not funny before the Doctor, who is sitting in the chair, begins talking about the book he has been looking at, saying he cannot find Wally in it anywhere. He asks Rupert if he is scared, to which he admits that he is. The Doctor explains that being scared is good. Being scared is like having a superpower; the blood and oxygen rushing through the body allows the person to run faster, fight harder, jump higher, and because he is so alert it feels as though he can slow down time. He then asks if the person underneath the cover is scared, to which he self-proclaims "Nah!".

The Doctor tells Clara and Rupert to turn their back to the person and look out of the window. The Doctor postulates that it is either a friend playing a joke on Rupert or it is something else. When Clara asks if there is a plan, he addresses the person under the covers and requests that whoever it is leave in peace. He makes the promise that if the person leaves they will not look. The person moves towards the trio and Rupert turns his head momentarily before the Doctor tells him to turn back around and for all three to close their eyes so as to prove that they will keep to their word and not look. He makes them promise that they will never look. After a moment, the person leaves (taking the cover) and the three turn around. Clara tries to calm Rupert down while the Doctor continuously makes unhelpful comments; eventually she tells him to shut up. Clara finds a box of plastic toy soldiers and puts some of the small figures around the perimeter of the bed to guard Rupert. She grabs one, proclaiming it the leader. When Rupert points out that it is broken and has no gun, Clara indicates that it is so brave it doesn't need a weapon, and that is why it is the boss. When she asks what the leader's name should be, Rupert replies "Dan. Dan, the soldier man.” Rupert asks Clara if she will read him a story to help him sleep, to which the Doctor walks forward and begins “Once upon a time...” before placing a finger on Rupert's head and rendering him unconscious, saying “The end”.

Back inside the TARDIS the Doctor asks Clara why they wound up there as the TARDIS was locked on to her timeline. She insists it was because she got distracted and lies when the Doctor asks if she has any connection to Rupert. When Clara later asks if he will remember this, he says that he scrambled his memory and will dream about Dan, the soldier man. Clara, disappointed, asks the Doctor for a favour and has him drop her back off earlier in the evening to the moment she left the restaurant. Waiting until her earlier self has gone, Clara goes back inside.

Clara and Danny apologise and Clara starts over by reintroducing herself. When he says that his name is Danny Pink and says that it is a stupid last name she tells him that she likes the last name. When he says that she can have it she jests and says it is a bold offer. He stammers and wonders why he is at a loss for words. She continues on and says Clara Pink would be a bit much, but then contrasts it with "Mind you; Rupert Pink." He asks how she knows his original name and she lies and says she heard someone from the school mention it. When he rebuts her lie by saying he has not mentioned that to anyone in years she insists that she heard it from someone and he asks if she is playing a joke on him. She insists that nothing about this is a joke. As she says this a man in an orange spacesuit walks in through the kitchen of the restaurant. Danny asks Clara where her coat is as she had put it on when she walked out minutes earlier. Distracted by the man in the spacesuit and Danny's defensive questioning, she admits that she needs to be honest about something. When he inquires that she be honest about everything, she says that would be a lot. He insists that it is weird and he does not "do weird". She says it is not weird and asks him to stay. He requests that, however weird the truth may be, she be honest as he can tell she is lying. She continues to insist that it is not weird, but is distracted by the man in the spacesuit who beckons that she follow him into the kitchen where the TARDIS can be seen parked. Danny says that he has had enough and walks out.

Clara follows the spaceman into the TARDIS and, believing it is the Doctor, scolds him for distracting her and creating further problems for her. The spaceman removes his helmet and she is surprised to see that the man looks like an older version of Danny. The Doctor explains that he is Colonel Orson Pink, and comes from approximately one hundred years in her future. When Clara inquires how the Doctor found him, he says that he reactivated the trace memories left over from her subconscious and the TARDIS brought him to the end of the universe where Orson had gotten stuck on an expedition where, when mankind meant to send a man through time by one week, he got sent to the end of time by mistake and had been stranded for six months. The three of them have travelled back to the end of time to Orson's capsule and the Doctor presses Clara again about how they could share a connection. At the same time the Doctor notes that Orson has locked his capsule, even though by now there is no-one left alive in the universe. Orson is adamant about not speaking about it, but the Doctor believes that the creatures have survived and now that no-one else is left they have no more reason to hide. He agrees to take Orson home, but tells him they spend one more evening there (under the pretence that the TARDIS needs time to recharge).

Orson begins packing his belonging into the TARDIS and he and Clara talk as she helps him. When she puts down his backpack, a package containing the toy soldier "Dan" falls out. Orson explains that it is simply a family heirloom that is meant to be passed down for good luck, expressing that it worked since he has actually been rescued. Clara advises him that when he gets home he stay away from time travel. He says that time travel runs in the family and, when probed about what he means, he says that there were stories about his great-grandparent. She presses him about what he means and why he asked her earlier if Clara knew who he was. He passes her the toy soldier in response. She states that it was a family heirloom to which he simply responds "Yeah."

Outside the TARDIS, the Doctor and Clara wait for night to fall. The lighting inside changes and the written words “DON'T OPEN THE DOOR” appear on the locked door. The Doctor states that the writing is only visible at night, and that Orson likely wrote it because while he is terrified of what is outside, six months of solitary confinement could lead to temptation to have company. The two make banter to pass the time and the Doctor inquires about who she was going on a date with. Their conversation is cut short by noises outside, including what sounds like a shriek. Clara asks the Doctor for a "comforting" explanation. He says that it may just be the hull cooling.

When Clara asks why they do not just leave if there is possible danger, the Doctor says that he is curious to know what the creatures are that remain out of sight, and that this is his best chance of seeing them. They hear banging on the door in increments of three. The Doctor recites a nursery rhyme and Clara asks what drove this obsession to learn their identity. With no direct reply, the Doctor uses his sonic screwdriver to unlock the seal to the door. The handle begins turning. The Doctor says that all he did was unlock it. Perhaps it is simply an automatic sequence on the pressure door when it is unlocked. Or perhaps is it company... The Doctor demands that Clara get in the TARDIS, but when she refuses to leave him outside alone he threatens that if she does not do as he says she will never travel with him again. Upset, she goes inside as the Doctor waits for the creatures to come in.

From inside the TARDIS, Clara and Orson watch on the monitor screen to see what is taking place. The monitor begins to malfunction once the door opens, but it clears up enough to show that the Doctor is holding onto the capsule's control console as the air shell has been breached. Orson steps out and rescues him. They place the Doctor, who is unconscious, down on the chair and note that he has a bump on his forehead. Orson says that any amount of the debris could have done that while Clara wonders if perhaps it was the creatures. Suddenly, there is movement at the doors of the TARDIS. Orson says that it is probably the rest of the atmosphere escaping the ship. Clara says that Orson says "probably" a lot. Orson asks if anything can get inside and, with the Doctor unconscious, she is uncertain. The Cloister Bell sounds. Worried, Clara places her hand in the telepathic circuits and hopes that it will take them out of harm's way. As they launch, Clara notices that the Doctor stirs momentarily. They land somewhere else and Clara steps outside into a barn. At the top of a ladder, there is a loft with a bed where a child underneath a shadow is crying. She gently calls out, asking if it is Rupert or perhaps Orson, but the person continues to cry. She is interrupted when a man and woman step inside the barn, forcing Clara to hide underneath the bed. The man does not understand why the boy does not want to sleep inside, but the woman says that he does not want the other boys to know that he is crying. The man wonders why he cries all the time. The woman says, "You know why", to which the man says that there will be no crying in the army. They approach the boy and the woman tells him that he can come inside any time he pleases, and she will leave the latch on the door whenever he is ready. As they leave, the man says that the boy cannot simply cry and run away whenever it pleases him if he is to join the army. The woman says the boy does not want to join the army, to which the man says that he is not going to be welcomed in the Academy either and that he will never make a Time Lord... Clara suddenly understands where she is as the boy continues to cry: the TARDIS has taken them back in time into the Doctor's childhood.

Inside the TARDIS, the adult Doctor wakes up wondering where they are. He asks Orson where Clara is and calls out her name. Outside, this prompts the boy to ask who is out there and step off the bed. Instinctively, Clara grabs his ankle from under the bed. Realising she is acting out the nightmare they have been investigating, she tells him that it is okay and this is merely a dream. All will be fine if he lies down and goes to sleep, and she asks him to do just this. The boy climbs back on the bed, but continues to cry. Clara sits down, strokes his head, and tells him to "Listen..."

Meanwhile Orson is asking the Doctor what it was that he saw at the end of the universe. Before the Doctor can say a word, Clara returns to stop him and postulates about whether or not it was anything at all. She believes that this fixation stems from the fact that maybe the Doctor does not want to admit that he is afraid of the dark. The Doctor goes to see where and when they are, but Clara tells him not to investigate. She asks him to promise her that they will take off and never look at where they have just travelled to. The Doctor asks why but she tells him not to ask questions and to take off. The Doctor refutes this by saying that he does not take orders, but she sternly says "Do as you're told." The TARDIS dematerialises from the barn and the youngster who will become the Doctor sits up from his bed. A flashback shows what Clara told the young Doctor: that this entire experience is a dream but that very clever people can hear dreams and to "please listen". She says that she knows that he is afraid and that fear is a superpower. Fear makes a person faster, more clever, and stronger. One day, he is going to return to this barn (as the War Doctor, when contemplating using the Moment) and he will be very afraid. But it will be okay because if he is wise and strong, fear does not have to make him cruel or cowardly, but it will make him kind instead. It makes no difference what is under the bed or in the dark as long as he knows that it is okay to be afraid of it. If he listens to nothing else, just listen when she says that while he is always going to be afraid, even if he learns how to hide it, fear is like a constant companion. This is good because it can bring people together, and fear can lead you home. Before she goes she leaves the toy soldier “Dan” by his bed to remind him that fear makes companions out of everyone.

As Clara gives her speech to the young Doctor, the two of them take Orson back to his own time. While travelling back to her time she hugs the Doctor, who protests. She arrives at Danny's home and, after both apologise to each other, they kiss. Back in the TARDIS the Doctor, seemingly satisfied, underlines the word "LISTEN". Back in the barn as a child, the young Doctor looks at the stars as he sees the toy soldier 'Dan', the leader who is so brave he does not need a weapon.

Cast

 * The Doctor - Peter Capaldi
 * Clara - Jenna Coleman
 * Danny Pink - Samuel Anderson
 * Rupert Pink - Remi Gooding
 * Reg - Robert Goodman
 * Figure - Kiran Shah

Uncredited

 * Orson Pink - Samuel Anderson
 * Young Boy - Michael Jones

The Doctor

 * The Gallifreyan man who visited the young Doctor in the barn was sceptical of him joining an academy, referred to simply as "the Academy", and becoming a Time Lord, believing he would join the army instead.
 * Clara Oswald has affected the Doctor's timeline since his childhood. She also gave him Danny Pink's toy soldier.
 * The Doctor in his youth didn't want "the other boys" to hear him cry, so he slept in a barn.

Individuals

 * Clara says she has never before been to Gloucester.
 * Courtney Woods is a pupil of both Clara and Danny.
 * Danny's birth name was Rupert. As a child, in the 1990s, he lived in the West Country Children's Home in Gloucester.
 * Clara uses plastic toy soldiers to "protect" under Danny's bed.
 * Danny dug twenty-three wells when he was a soldier. He stresses that this was an important part of his work, and is clearly disturbed by other aspects of being a soldier, in particular killing people.
 * Colonel Orson Pink is the first recorded human to time travel, about a hundred years after the 2010s. His original destination was "next Thursday".
 * Clara connects to the TARDIS' telepathic circuits twice, first to return to the time of her nightmare (though she ends up being distracted and taking the TARDIS to the time of Danny's encounter with the nightmare), then to pilot the TARDIS to Gallifrey. The latter marks the first time Clara is shown piloting the TARDIS autonomously in any way.
 * Clara has three vanity mirrors.
 * Clara becomes one of only a select few companions to actually see an earlier version of herself. She expresses approval of her figure, though she later tells Orson that meeting yourself can be "embarrassing."

Cultural references from the real world

 * The Doctor is looking for Wally in a book. Rupert explains that not every book is a Where's Wally? one.

Laws of Time

 * Clara wonders if asking to be brought back in her recent past might break the laws of time. Indeed, she arguably breaks the First Law of Time by crossing her own timeline, though her earlier self is never made aware that she is being observed.

Story notes

 * Aside from archive footage, and body/voice doubles, this episode marks the first time in years that the First Doctor had appeared in an episode of the show, as well as being played by a different actor (he has now been played by four different actors). It also marks the very first instance the Doctor has been portrayed as a child in the televised series. The Doctor is the second Time Lord (not including the children in The Day of the Doctor) to be shown as a child; the first one was the Master, in The Sound of Drums.
 * Samuel Anderson appears as both Danny and Orson Pink, but was credited only as 'Danny Pink' both on-screen and in Radio Times.
 * The Radio Times programme listing was accompanied by a small head-and-shoulders shot of Samuel Anderson as Orson Pink, with the (inaccurate) accompanying caption "Doctor Who / 7.30 p.m. / Suited up to explore space and time: former soldier Danny Pink (Samuel Anderson)".
 * In a 2007 short story, Corner of the Eye, Steven Moffat had already dealt with the idea of monsters who had the super-ability to hide (called Floofs). Previously, he had revived concepts from his short story What I Did on My Christmas Holidays by Sally Sparrow into his televised Blink.
 * The Doctor seems to have either forgotten he watched over Clara's life or thinks they've arrived in the childhood of one of her echoes.
 * The thing beneath the sheets on Rupert's bed has, as of 2018, never been revealed.
 * The only reason that the TARDIS ended up in the Doctor's past is because several safety measures were turned off by the Doctor to search for the creatures.

Ratings

 * 7.01 million (DWM 479)

Filming locations

 * The Rest, Porthcawl
 * Mimosa Kitchen & Bar, Mermaid Quay
 * Bute Park, N Rd.
 * Whitchurch, Cardiff

Production errors

 * Orson Pink has a Sanctuary Base Six (TV: The Impossible Planet) badge on his spacesuit - a site which was not established for another two thousand years. And it cannot be the Doctor's suit, as it's seen in the news footage before he time travels, albeit with the logo not clearly visible.

Continuity

 * Clara's encounter with the Doctor as a young boy marks at least the second time that a version of her has met his original incarnation, and the first from his perspective. One of the splinters created after she entered the Doctor's time stream had met the older First Doctor, suggesting to him which TARDIS to steal as he escaped Gallifrey. (TV: The Name of the Doctor)
 * The barn that the young Doctor seeks shelter in is the same one the War Doctor goes to in order to activate the Moment. (TV: The Day of the Doctor)
 * The Twelfth Doctor continues his habit of using chalk. (TV:  Deep Breath, Into the Dalek, Robot of Sherwood)
 * By removing the safeguards, the TARDIS goes farther forward in time than it normally would. (TV: Frontios, Utopia)
 * The Doctor has previously visited the end of the universe. (AUDIO: Singularity, The Judgement of Isskar, TV: Utopia)
 * The Twelfth Doctor uses his psychic paper for the first time in this incarnation. (TV: The End of the World onwards)
 * The Doctor uses mind control (TV: The War Machines et al.) to make Rupert Pink sleep and scramble his memory about their rendezvous, by pressing his finger against his forehead.
 * The Doctor has met other humans who have experimented with time travel, most originating from farther in the future than Orson. (TV: The Talons of Weng-Chiang, The Empty Child, Hide)
 * The Doctor finds Orson Pink thanks to a trace left by Clara Oswald in the telepathic circuits of the TARDIS. (TV: Frontier in Space et al.)
 * The spacesuit Orson Pink wears is similar to the spacesuits in the Sanctuary Base 6 on Krop Tor, and even has the same logo. (TV: The Impossible Planet, The Satan Pit)
 * The Twelfth Doctor, upon awaking in the TARDIS, mentions "Sontarans perverting the course of human history" to Orson Pink, repeating his first words as the Fourth Doctor (TV: Robot), who was describing events which had recently been experienced by the Third Doctor. (TV: The Time Warrior)
 * The Doctor references being a father. (TV: An Unearthly Child, Fear Her, The Doctor's Daughter)
 * Clara's words "one day you're going to come back", “fear makes companions of us all” (TV: An Unearthly Child) and “do as you're told” (TV: The Daleks' Master Plan), are phrases the Doctor would use early in his travels.
 * The Twelfth Doctor states that there is nothing to hear, "not a click or a tick", something previously stated by the Third Doctor. (TV: Death to the Daleks)
 * Clara's words "fear doesn't have to make you cruel or cowardly" echoes what the Doctor told her was the "promise" related to his name. (TV: The Day of the Doctor.)
 * Discounting TARDIS-orchestrated scenarios, Clara becomes the ninth (known) companion to glimpse or encounter themselves in the past or future after Jo Grant (TV: Day of the Daleks), Brigadier Lethbridge-Stewart (TV: Mawdryn Undead), Romana (AUDIO: Luna Romana), Peri Brown (AUDIO: Peri and the Piscon Paradox), Rose Tyler (TV: Father's Day), Amy Pond (TV: The Hungry Earth / Cold Blood, The Big Bang), Rory Williams (TV: The Hungry Earth), and River Song (TV: The Impossible Astronaut, The Wedding of River Song).
 * Like Amy Pond (TV: Time), Clara admires herself. Her remark about how she looks from behind mirrors the Tenth Doctor remarking how rare it was to see the back of his own (i.e. Fifth Doctor's) head (TV: Time Crash), though Clara's assessment is more positive. This is not, however, the first time Clara has seen herself. (HOMEVID: Clara and the TARDIS)
 * When Clara asks if it would be dangerous for her to meet her younger self, the Doctor tells her it would be "potentially catastrophic". (TV: Day of the Daleks, Mawdryn Undead, Father's Day)
 * The Doctor is able to sit on the roof of his TARDIS to meditate in the quiet vacuum of space without suffocating because the TARDIS can extended her air shell. (TV: The Horns of Nimon, The Time of Angels, The Beast Below, The Time of the Doctor)
 * When the TARDIS appears to be in jeopardy, the Cloister Bell begins to sound. (TV: Logopolis onwards)
 * The First Doctor sleeps alone in the barn, echoing the Ninth Doctor's comment to Nancy that he knows what it's like to be a child left alone in the cold. (TV: The Empty Child) Madame de Pompadour also commented on his childhood loneliness when the Tenth Doctor linked minds with her. (TV: The Girl in the Fireplace)
 * The telepathic circuits of the TARDIS were used early in the Doctor's travels to warn him and his companions of impending danger. (TV: The Edge of Destruction)
 * The telepathic circuits were previously mentioned before in COMIC: The Tomb of Shemura. Later on, Simon would also use them. (PROSE: When the Wolves Came)
 * The Eleventh Doctor once said it was good to be scared in dangerous situations. (TV: The Time of Angels)
 * The Doctor says once again that he's against hugging. (TV: Deep Breath) He would later give a reason for this. (TV: Death in Heaven)
 * The Doctor has taken Clara to the far future where everything she knows is long dead before (TV: Hide).

DVD releases

 * The episode was released as part of the Complete Series 8 box set in November 2014. 

Blu-ray releases

 * The episode was again released as part of the Complete Series 8 box set in November 2014.

Digital releases

 * The episode was released on Google Play, iTunes and Amazon Instant Video in HD or SD, also available as part of the Series 8 digital boxset. The digital boxset contains various features: trailer, interviews, The Ultimate Companion, The Ultimate Time Lord, Inside the World Tour and Doctor Who Extra episodes for each episode.
 * In the US, the series was released through digital streaming services Hulu and Netflix with a subscription.
 * In 2015, it was released by BBC Worldwide on BitTorrent and iTunes, in A Decade of the Doctor bundle to celebrate the 10th anniversary of the new series. It included introductions by Peter Capaldi, Earth Conquest: The World Tour and an episode guide.