The Impossible Astronaut (TV story)

The Impossible Astronaut was the first episode of the sixth series of Doctor Who. This story is perhaps most notable as the first opening two-parter of the BBC Wales series. Behind the scenes, it was notable for the significant amount of location filming with cast and crew travelling to Utah in the United States of America.

Narratively, it saw the reappearance of River Song with some insight into her back story. Yet again, questions of her trustworthiness were posed. Additionally, it built on the references of the previous series to "the Silence".

Synopsis
Four envelopes, numbered 2, 3 and 4, each containing a date, time and map reference, unsigned, but TARDIS blue: who sent them? And who got the missing envelope numbered 1? This strange summons reunites the Doctor, Amy, Rory and River Song in the middle of the Utah desert and unveils a terrible secret the Doctor's friends must never reveal to him. Placing his life entirely in their hands, the Doctor agrees to search for, and figure out just who is, Canton Everett Delaware the Third. What is the relevance of their only other clue: 'Space 1969'? Their quest lands them—quite literally—in the Oval Office, where they are enlisted by President Nixon to assist former-FBI agent Canton in saving a terrified little girl from a mysterious spaceman.

Plot
In the 17th century, Charles II furiously bursts into his daughter's room, demanding to know where the Doctor's location. By her stands "My Mysterious Doctor," a painting of the Time Lord covering himself with a red cloth; his clothes are strewn about the room. She asks, "Doctor who?" in an embarrassed tone. Before she can speak further, a loud sneeze comes from beneath her skirt. The king lifts its hem with his sword to find the Doctor naked underneath. With the king scowling at him, the Doctor explains that things are not as bad as they look.

In 2011, Amy Pond reads to her husband, Rory Williams, from a history book in their home; it is an account of "a mysterious doctor" imprisoned in the Tower of London on order of the king, without trial. Rory doubts it is the Doctor until Amy reads he was seen flying away from the Tower two days later via a magical sphere. Amy then notices there's more of the Doctor's exploits.

The Doctor is next seen taking part in a break-out from a POW camp during World War II. When the Doctor is asked by a fellow escapee if they have gotten past the fence, the Doctor pops his head down a duct. He asks if the Commandant's room is green with a big flag on the wall as dogs and angry yells are heard. The Doctor figures the answer's "yes", as he's pulled back out by the Germans.

Amy wonders if the Doctor is being deliberately ridiculous to catch their attention - "waving through time". However, Rory shrugs the theory off as Amy complains about watching a Laurel and Hardy film again. The doorbell rings and Amy gets up to answer it. Rory looks in the book to see if Amy is right, missing a part of the film where a fez-wearing Doctor dances with the characters. Receiving their mail, Amy goes through it to find a TARDIS-blue envelope plastered with stamps and labelled with the number 3. It holds an unsigned card with a map reference, date and time. They easily deduce it's from the Doctor.

In the 51st century, River Song has an identical letter, marked number 2, delivered to her cell at Stormcage Containment Facility. Upon reading it, she smiles. The prison goes on alert as soon as they find River packing her belongings (again). When questioned about where she's going, River tells them she's heading for America (in the 21st century). The guards mistake America for a planet when informing the warden.

In the middle of the Utah desert, Amy and Rory depart a bus, finding nothing around them until the bus leaves. They are happily greeted by the Doctor, now wearer of a Stetson. After exchanging greetings, Rory compliments the Doctor's hat. Just as the Doctor explains it's the latest in his "cool" ensemble, his hat is shot off by River, who promptly greets him.

At a cafe, the Doctor and River compare diaries, finding that they have both had an adventure at Easter Island and met Jim the Fish. Rory becomes confused until Amy clears up why they are comparing diaries. Amy then asks why the Doctor summoned them to America. The Doctor explains that he has been running faster than he's ever been, but he's decided to stop; they are going to have a picnic and then go on a trip to "Space 1969".

They picnic by a lake, where they drink wine; the Doctor spits it out in disgust, commenting he's 1103 years old -- nearly two hundred years older than when Amy and Rory last saw him. Amy spots a figure watching them from a distant cliff, but forgets about it when she looks away. Not long after, an elderly man pulls up in a truck and waves, but makes no move to join them. The Doctor seems to know who the old man is and waves back.

River gasps, "Oh my God", while everyone else is facing the old man. The three of them turn around to see an astronaut rising out of the water, wearing an Apollo 11-style spacesuit. Spotting it, the Doctor orders his friends that they're not to interfere no matter what happens. He approaches the astronaut, who waits for him at the edge of the lake. Letting the wearing of the suit know he already knows their idenity, the astronaut's visor is lifted, but the face of who's inside is left unknown to the audiance. The Doctor talks with the atronaut for a bit, leaving his companions confused as to what they're doing. The astronaut raises its arm and shoots the Doctor twice.

Amy tries running to the Doctor, but River and Rory restrain her. The Doctor picks himself up as Amy calles out to him; he's begun his eleventh regeneration. He appologizes to his friends and prepares to regenerate. However, the astronaut shoots him in mid-process, killing him before his transformation could complete. As the astronaut heads back into the lake, River scans the Doctor, finding he's dead, and empties her gun shooting at the astronaut, failing to get a hit. Amy is distraught, hoping the Doctor is only playing dead or that it is a clone/copy of him.

However, the stranger approaches and says that the Doctor is truly dead, placing a container of gasoline next to them; the Doctor told him they would need it. River explains that a Time Lord's body is one of the most sought-after things in the universe. They can't just leave him. Spotting a boat moored across the lake, Rory performs a Viking-style funeral to burn the Doctor's corpse. River wonders who the old man is and he shows them he got number 4 of the invitations. Greeting Amy, Rory and River by name, the old man introduces himself as Canton Everett Delaware III, explaining he will not see them again, but they will see him.

Seeing the number on Canton's invitation, River begins pondering who got number 1. Explaining things as they return to the cafe, River is left to wonder who else the Doctor invited. Rory and River want to know what the Doctor planned. Amy insists that it doesn't matter anymore, but because it mattered to the Doctor, Rory and River say it's important to them. Across the cafe, Rory spots another invitation on a table, labelled number 1. It must be addressed to the person the Doctor trusted most; River wonders who it is.

Much to their shock, the Doctor steps out of the back room, which is where the TARDIS is parked. He greets them happily, surprised they are all here. River slaps him in fury, prompting him to ask if it's for something he hasn't done yet. They wonder how he can be there and the Doctor explains he got invited like they did. With Amy and Rory still confused, River asks the Doctor to tell them his age, which is 909; he has not even met Jim the Fish yet. River says they've been hired by someone who trusts him to investigate something involving space 1969, and a man called Canton Everett Delaware III. When the Doctor asks who hired them, River simply answers, "Spoilers".

In the TARDIS, the Doctor prepares to enter the clues River gave him into the TARDIS navigation system. River and Amy go under the console floor. When the Doctor asks Rory if they're mad at him, Rory follows after. Out of earshot, River explains to Amy that they saw a future version of the Doctor die at Lake Silencio; they cannot tell this Doctor of his coming death. As he has interacted with his own tim stream, any foreknowledge could rip a hole in the universe should he find out. They are the left to wonder why they were recruited, wondering if it was to avenge him, save him, or something else.

The Doctor calls them back up, complaining that he is being utterly brilliant and noone's around to look impressed. After River explains to Amy that there is a worse day coming for her, all three head back up to the Doctor. He explains that the clues he was given lead the TARDIS to the Oval office 1969, April 8th. However, he says that he is returning Amy and Rory home while River is going back to prison. He explains that he will not go on a mysterious summons, wondering who sent them and why.

River tries to get the Doctor to trust them, but he turns the tables on her by asking who she is and who she killed to get imprisoned in Stormcage; he does not trust her. Amy then asks the Doctor to trust her instead, saying he must go on the summons and not ask why. The Doctor questions Amy to see if she's been threatened to say this, but she says no. He then asks her to swear on something that matters, to which Amy says, fish fingers and custard, their first shared meal.

He sets the TARDIS for 1969, checking to see who's president during that time, learning it's Richard Nixon, not exactly his favourite due to the events that happened during his time as president. River calls him a hippy for such views. The Doctor tells his companions that he is going to turn the TARDIS invisible and put it on "silent" to avoid drawing attention. However, each time he flips switches to initiate the process, River uses other ones to turn off loud noises and lights he activated by accident.

On landing, he calls for discretion and exits alone as the monitor doesn't work while the TARDIS is invisible. He has landed it in the Oval Office, where Nixon is meeting with a younger Canton Delaware. Nixon wants Canton to conduct an investigation independent of the FBI, from which Canton was recently fired, to find a child who has been calling him every night, begging for help because the "space man" is coming to eat her. Nixon plays Canton a recording of a call, in which Nixon asks the child where she is and her name. The child answers, "Jefferson Adams Hamilton", which led Nixon to believe a little boy was the caller. Canton feels the FBI can handle this, but Nixon fears they may be in on it, which is why he called him in; he's not with them, but has the training.

The Doctor, who has been taking notes, then notices that they have stopped talking and realises that they have seen him. The Doctor begins rambling as he backs up to the TARDIS. However, he bumps into it, knocking himself down. Inside, River complains about how he does this "every time". The Doctor explains the doors getting stuck happens commonly while the TARDIS is invisible. However, Canton pins him down as Secret Service agents swarm the office.

River gets the monitor working by hard-wiring it. As the monitor displays the Doctor, he asks River if she's gotten the monitor working again. After the usual, "I hate him/No you don't", River makes the TARDIS visible again, allowing the Doctor to be freed of the Secret Service holding him down.

The Doctor says he will take the case. However, he taunts the Secret Service by saying he broke into the Oval Office. River comes out of the TARDIS, reminding him they're Americans, prompting the Doctor to tell them not to shoot. Amy and Rory depart the TARDIS as well. When Nixon questions who they are, the Doctor claims to be an undercover agent on loan from Scotland Yard while his companions Amy, Rory and River are his top operatives: the Legs, the Nose, and Mrs Robinson.

Explaining that he figured out where the caller is from what Canton and Nixon heard, the Doctor aks for five minutes to figure out the case. Depsite protest from the head of the Secret Service in the office, Canton decides to give the Doctor his alloted time, promising to shoot him if he doesn't deliver a solution. The Doctor asks for a SWAT team ready to mobilise, street-level maps covering all of Florida, a pot of coffee, 12 Jamie Dodgers and a fez. However, he is only given his maps. When questioned, "why Florida," the Doctor explains that's where NASA is, where the spacemen live; he's also following another lead.

While researching the street maps, Amy sees a mysterious, suited alien standing in the doorway of the Oval Office, and remembers their encounter on the shore of the lake. However, she forgets as soon Rory blocks her view. Feeling ill, she is escorted to the bathroom, where she finds the alien waiting for her. A woman who is also in the bathroom is vaporised by the alien after seeing and forgetting it numerous times. Amy, realising the alien's power, takes a picture of it with her camera phone. It cryptically informs her that she will tell the Doctor, "what he must know, and what he must never know". Amy flees and immediately forgets the encounter, but remembers there is something she needs to tell the Doctor.

In the Oval Office, the Doctor achieves success, pointing out that it's pretty obivous to figure out where the caller is when you think about it. Canton calls the Doctor a genius, which the Doctor says is a hobby. Nixon gets another call form the child, saying that a spaceman is coming to eat her. Fearing for the girl's life, the Doctor decides that there's no time for a SWAT team and departs with his companions in the TARDIS while Canton tails along after being told not to follow them in - reverse psychology.

In the TARDIS, the Doctor explains that Jefferson, Adams and Hamilton are the names of three of America's founding fathers; two of them fancied the Doctor. However, neither of them is the child's name. At the same time, Canton is bewildered by the inside of the TARDIS and is left speechless. Upon landing, Canton blocks the way and the Doctor, Amy and River leave Rory to explain things to Canton as he's the newest companion. Canton asks Rory, "Doctor who?" They've materialised in a warehouse in Florida, just a few miles from Cape Kennedy; Jefferson, Adams, and Hamilton are the three streets which cross right outside the window. As they explore the warehouse, the Doctor admits they have likely walked into a trap and the phone line has been cut, leading to the question as to how the girl called from there. Meanwhile, Rory attempts to explain the TARDIS and time travel to a stunned Canton, who eventually recovers.

They discover a console made of cables, coated in some sort of slime, and many boxes of Apollo space equipment. Amy suggests to River that they find some way to kill the astronaut now to prevent it from killing the Doctor in the future. River admits time can be rewritten, but it is very complicated and doesn't work in the way that Amy hopes, so there's no guarantee that the Doctor can be saved.

River finds a drain leading into a tunnel network below the warehouse. Below, she sees many hibernating aliens, the same ones Amy interacted with. She forgets them as soon as she climbs back to warn the Doctor. She says that it is safe but that she wants to take another look, perhaps out of a subconscious reminder. The Doctor sends Rory down with her this time to make sure she stays safe.

They discover a maintenance room, which River proceeds to open with her scanner. River explains her relationship with the Doctor; their timelines are mostly going in opposite directions of each other, meaning each time she meets him, he knows her less. She fears one day she will meet the Doctor and he will have no idea who she is.

She succeeds in unlocking the door, opening it to find a large control console like the TARDIS and the one that the Doctor encountered during his stay with Craig Owens. River tells Rory to keep a look out for anything odd. Rory sees some of the aliens, but when he turns to tell River, he says everything is okay. Scanning the console, River learns that there are tunnel like the one they're in all over Earth and that they've been here thousands of years. Behind Rory, electricity crackles and something approaches.

Above, Canton and Amy discuss the former agent's FBI career; he was kicked out because he wanted to get married. He questions her relationship with the Doctor, but Amy explains that he is only her friend and there was something important that she wanted to tell him, but seems to have forgotten. Canton then wonders who the Doctor is, but Amy tells him it's classified. When he asks by who, Amy can only say, "God knows", as she has no idea. They hear the little girl calling for help and run after her. Amy crumples with pain while Canton runs ahead.

As they run after Canton, they find him unconscious; he got a good blow to the head. As the Doctor examines Canton to see if he's been badly injured, Amy tells him that she's pregnant. Before he reacts to this, he spots the astronaut approaching them. Amy recognises it from the lakeside and turns to pick up Canton's gun. Her back is turned when the the astronaut lifts its faceplate, revealing the little girl is inside. Amy spins to shoot the astronaut, but is unable to stop when the Doctor tells her to and when she notices it's the little girl.

Cast

 * The Doctor - Matt Smith
 * Amy Pond - Karen Gillan
 * Rory Williams - Arthur Darvill
 * River Song - Alex Kingston
 * Canton Delaware - Mark Sheppard
 * Old Canton Delaware - William Morgan Sheppard
 * President Richard Nixon - Stuart Milligan
 * Carl - Chukwudi Iwuji
 * Phil - Mark Griffin
 * The Silent - Marnix Van Den Broeke
 * Little Girl - Sydney Wade
 * Joy - Nancy Baldwin
 * Prison Guard - Kieran O'Connor
 * Captain Simmons - Adam Napier
 * Matilda - Henrietta Clemett
 * Charles II - Paul Critoph
 * Busboy - Emilio Aquino
 * Young Couple- Alexus Koors & Benjamin Wright

The Doctor

 * An older Eleventh Doctor, who is eleven hundred and three years old, begins to regenerate, but is killed before the process completes.
 * The younger Doctor states his current age is nine hundred and nine.
 * The Doctor says that he is late for a biplane lesson in 1911 but gets confused and wonders if it is actually knitting.
 * The Eleventh Doctor still dislikes wine.
 * The Doctor claims that two of the American founding fathers mentioned in the girl's message fancied him, although he does not identify which two.
 * In The Wedding of River Song, it is shown that the Doctor was actually the Teselecta in his form.

Music

 * When the Doctor, Amy, Rory and River are in the diner before going to Lake Silencio, "Rolling in the Deep" by Adele is playing in the background.

Films

 * Amy Pond and Rory Williams watch a Laurel & Hardy film, The Flying Deuces, on television.
 * This story shares numerous similarities with the 1988 John Carpenter film They Live, in which the primary protagonist discovers a hidden alien race living amongst humans, using subliminal messages to influence their development.
 * The Doctor refers to River Song as Mrs. Robinson - a character from the 1967 film The Graduate.

Fashion and clothing

 * The Doctor wears a fez in a Laurel & Hardy film, The Flying Deuces.
 * The eleven hundred three year old Doctor wears a Stetson hat, and proclaims that "Stetsons are cool". As with the last time he tried to adopt headgear, it is promptly dealt with by River Song's gun.
 * The eleven-hundred and three year-old Doctor who dies in the beginning of the episode is wearing a purple bow-tie and purple braces as opposed to his usual maroon or turquoise. This is likely an Easter-egg for keen-eyed viewers to indicate that this is not the real Doctor.

Foods and beverages

 * The Doctor thought wine would taste more like 'the gums', referring to wine gums.
 * The Doctor asks for twelve Jammy Dodgers.

Years

 * The Doctor states that the year 1482 is full of glitches, but also says 1969 is 'easy'. It seems some years are harder to travel to than others.

TARDIS

 * The Doctor makes the TARDIS invisible when he materialises in the Oval Office. The Doctor states that this causes a huge drain on the TARDIS energy. When he tries to re-enter the TARDIS, he smashes into it.
 * The Doctor also manages to land the TARDIS silently.
 * The Doctor claims that the TARDIS scanner cannot be activated when the TARDIS is invisible. This is later shown to be false, as River makes adjustments inside the TARDIS and operates the scanner, as the Doctor's later dialogue indicates he had expected her to do.

Locations

 * The Doctor says that the people of Easter Island worshipped him when he and River visited. Easter Island is known for its huge stone statues of faces featuring, among other things, prominent chins.

Story notes

 * This episode had the working title The Year of the Moon.
 * This is the first two-part opening episode of the revived series.
 * A prequel for this story was released on the official BBC website.
 * The monsters in this episode were said to be "the scariest monsters yet".
 * The episode was dedicated to Elisabeth Sladen, who passed away four days before the episode's initial broadcast. The dedication was shown before the episode on BBC1 and Space, and after the episode on BBC America. The dedication was omitted from the DVD and Blu-ray release.
 * The version supplied for broadcast in the United States, Australia, Canada and Israel featured a voiceover introductory sequence before the main titles, with the voice of Amy explaining her relationship with the Doctor.
 * While the local date and time when the Doctor is killed is the evening of the 22nd April, 2011, the local date and time in Britain (a seven-hour difference from Utah) would be two minutes after midnight on 23rd April, as TV: Let's Kill Hitler establishes the point of death as 5:02pm local time. Thus, this is the third story in the revived series whose airdate coincides with in-story events (the first being TV: The End of Time on December 25, 2009, and the second being TV: The Big Bang on June 26, 2010).
 * The attempted regeneration in this episode occurs in front of six witnesses, the greatest number in the revived series (Amy Pond, Rory Williams, River Song, Canton Delaware, the astronaut, and a Silent).
 * This is the first episode of the revived series to feature a regeneration (albeit an unsuccessful one) outside the TARDIS.
 * The sequence with the Doctor inserted into the The Flying Deuces clip is a reference to the 1992 American Academy Awards. Host Billy Crystal was digitally added into the same clip and was depicted dancing alongside Laurel and Hardy. In this version, the Doctor begins to dance with Laurel and Hardy at the end of the clip, standing in the same spot that was occupied by Crystal.
 * The repeated phrase "Space: 1969" is a reference to the British science fiction series Space: 1999, which is set on the moon.
 * The Doctor asks the Secret Service agents for a SWAT team. The first SWAT (Special Weapons And Tactics) team had only been established the year before in 1968 (by Darryl Gates in Los Angeles) and it's possible the agents might not have even known what the Doctor was talking about.
 * The idea of tunnelling out of a German POW camp is based on actual incidents that occurred during World War II, immortalised in the film The Great Escape and parodied in the television series Hogan's Heroes.
 * Joy asks if the Silent is wearing a Star Trek mask. Star Trek was cancelled the same year this story takes place, with the last episode airing on June 3, 1969.
 * The Doctor calls River Song "Mrs. Robinson", referencing the character from the film The Graduate. Mrs. Robinson has an affair with a younger man, so the nickname may be the Doctor's way of teasing Song about their relationship and the fact that physically she appears to be older than he is. Oddly enough, the Doctor doesn't recognise the reference when River Song calls him 'Benjamin' (her lover) when reenacting the iconic Graduate scene in Let's Kill Hitler.
 * William Morgan Sheppard is the real life father of Mark Sheppard; the two have portrayed father & son pairs and, as in this episode, older & younger versions of the same character.
 * Alex Kingston and Sydney Wade had come off of filming Marchlands in which they played a mother & daughter, immediately prior to filming this episode in which they portrayed older & younger versions of Melody Pond/River Song.
 * The Silents bear a slight resemblance to the Gentlemen from Buffy the Vampire Slayer.

Ratings

 * 8.86 million. (43.3% market share)
 * Viewership for the episode on BBC America was 1.3 million, breaking the station's previous viewership record which had been set by the premiere of The Eleventh Hour.
 * The episode was the most recorded show in UK history with 4.1 Million viewers

Myths

 * We will see River Song as a child. This was proven true, but not stated until TV: Let's Kill Hitler.
 * The second episode will air the day after the first.  This has been proven false.
 * Overnight figures for BBC was 6.4 million making this the least watched series opener since the 2005 relaunch. Proven false. The Daily Mail and other places were comparing the overnight-only ratings of this episode to the full consolidated BARB ratings for the previous season openers, which include people watching time-shifted playback and recordings (such as with Sky+). The consolidated figures were 8.86 million, which compares favourably to other series openers.

Filming locations

 * Valley of the Gods, Utah, United States of America
 * Eddie's Diner, Cardiff Bay

Production errors

 * While the Doctor appears in the Laurel & Hardy film, The Flying Deuces, Rory's shifts through the pages of the history book which appear underneath the screen imply the film footage was overlaid on the actual shot.
 * When the Doctor approaches the astronaut he leaves the picnic with a wine bottle in his hand. In the next shot the bottle is gone.
 * While River is shooting at the astronaut, the Doctor's hands change position. His left hand, which was spread out to one side, is on his stomach when the shot changes. It swaps back and forth a couple of times.
 * The astronaut does not put their visor back up as they walk back into the lake.
 * When Amy is talking to the agent outside of the toilet, a boom mic can be seen over his shoulder.
 * When the Doctor exits the TARDIS control room he opens the right door but when he walks out to the Oval Office he goes out the left.
 * One of the mission patches on the astronaut's space suit is an anachronism; the "Vitruvian Emblem" was first used during the space shuttle missions of the early eighties.
 * The Secret Service agents all carry revolvers, which were more commonly in use during the period . However by 1969 the Secret Service had transitioned to the semi-automatic Colt M1911.
 * When Amy and Rory get off the bus, it drives away and then, when the Doctor and Amy hug, the bus is nowhere to be seen.
 * In the scene when the Silent gets ready to kill Joy, electricity can be seen flying into his body, but on the mirror next to him the electricity cannot be seen.
 * Canton Delaware offers another example of British usage by American characters. Referring to the TARDIS ability to travel in space and time and to be bigger on the inside, he asks, "How long have Scotland Yard had this?" An American would have said, "How long has Scotland Yard had this?"

Continuity

 * River Song shoots the Doctor's headwear. (TV: The Big Bang)
 * Amy mentions fish fingers and custard. (TV: The Eleventh Hour)
 * The Doctor requests Jammie Dodgers and a fez. (TV: Victory of the Daleks, The Big Bang)
 * The Doctor says that time isn't a straight line. (TV: Blink)
 * The Doctor again asks River whom she murdered. (TV: Flesh and Stone)
 * The Doctor again expresses his dislike of wine, despite drinking it. (TV: The Lodger).
 * River Song suspects that she will one day meet a Doctor who hasn't met her yet, and it will be the death of her. (TV: Silence in the Library / Forest of the Dead)
 * As of this episode, River and the Doctor are each aware of how the other (apparently) dies, though neither will say so to the other. (TV: Forest of the Dead)
 * River Song says, "I hate you", to the Doctor and he replies, "No, you don't". (TV: Forest of the Dead, Flesh and Stone )
 * The attempted TARDIS is seen again. (TV: The Lodger)
 * The Doctor looks at the front and then back of his hands before he is about to regenerate. (TV: The Parting of the Ways, The End of Time)
 * The TARDIS has previously been made invisible, and the Doctor has previously operated the scanner while it was. (TV: The Invasion)
 * The Doctor has landed the TARDIS silently before. (TV: The Dalek Invasion of Earth)
 * The danger of the Doctor's body being used as a commodity was seen in PROSE: Alien Bodies.
 * Rory pokes the Doctor and asks him, "How can you be here?", much as the Doctor did to him. (TV: The Pandorica Opens)
 * The Doctor says, "Brave heart, Canton", referencing the catch phrase, "Brave heart, Tegan", used by the Fifth Doctor.
 * In the Oval Office, the Doctor refers to Canton Delaware III as "Canton Three". This is a similar naming convention to the one used by Liz Ten for herself and earlier ruling members of the Royal Family. (TV: The Beast Below)
 * The Doctor says, "Human beings. I thought I'd never get done saving you", at the picnic, which echoes his line in Time of Angels: "You're like rabbits! I'll never get done saving you!"
 * When sitting at the President's desk, the Doctor says, "Mister President", in the exact same manner as Ramón Salamander (played by Second Doctor actor Patrick Troughton, a large inspiration for the Eleventh Doctor). (TV: The Enemy of the World)

Home video releases
Released as Series 6 Part 1 with Day of the Moon, The Curse of the Black Spot, The Doctor's Wife, The Rebel Flesh, The Almost People and A Good Man Goes to War on 11 July 2011.