As a show with over 50 years of rich history to draw upon, Doctor Who often includes throwbacks and Easter Eggs related to earlier episodes. For the current, tenth series of the revival — set to be the last for both current showrunner Steven Moffat and Twelfth Doctor Peter Capaldi — this is even more true. Here, I will compile a list of all the #EasterEggs in Series 10. Have you spotted them all?
Note: This article will be updated as each episode airs or new info becomes available. Some entries will contain SPOILERS.
Episode 1: 'The Pilot'
- The Doctor's desk has photos of both his wife (River Song) and his granddaughter (Susan). He also keeps a container of his old Sonic Screwdrivers.
- New companion Bill Potts is named after William Hartnell, the actor who played the First Doctor. Heather, the girl consumed by the puddle, is named after Hartnell's wife.
- When Bill first enters The Doctor's office, he is playing Beethoven's Fifth Symphony. This is a reference to the episode "Before The Flood," in which The Doctor uses the symphony to explain the Bootstrap Paradox to viewers.
- The blackboard that the Doctor uses has previously been seen behind Miss Quill in promotional pictures for the #DoctorWho spin-off Class.
- The Doctor, Bill and Nardole briefly visit a Dalek-Movellan War Zone. The Movellans have not been seen onscreen since "Destiny Of The Daleks" in 1979.
- Jennifer Hennessy, the actress playing Bill's foster mother, Moira, previously appeared as Valerie, the wife of Cat-man Thomas Kincade Brannigan, in the Tenth Doctor episode "Gridlock."
- When Bill asks the Doctor how it would feel if someone wiped his memories, the theme "Clara" is briefly heard. The Doctor knows exactly how it would feel because Clara Oswald unintentionally wiped his memory of her at the end of Series 9.
Episode 2: 'Smile'
- While singing the praises of the TARDIS to Bill, The Doctor tells her that it can offer "everything that has ever happened or ever will." This is the same line that The Eleventh Doctor uses to tempt Amy Pond into traveling with him at the end of "The Eleventh Hour."
- The Doctor's initial disappointment with the Emojibots — officially called the Vardy — echoes his general dislike of social media, seen in earlier episodes such as "The Girl Who Waited" and "Kill The Moon."
- The function of The Vardy (causing terror and death while believing that they are helping) seems very similar to the Handbots from the episode "The Girl Who Waited."
- As Bill is eating her futuristic algae meal, The Doctor tells her that he is "not fond of fish, except socially." This is probably a reference to Jim the Fish, an often mentioned but never seen character from The Doctor and River Song's adventures together.
- While discussing how he can be Scottish with Bill, The Doctor states that they fly around "demanding independence from any planet they land on." This is a throwback to the episode "The Beast Below." On board Starship UK with The Doctor, Amy asks where Scotland is, only to be informed that they wanted their own ship.
- "Smile" could be seen as a sequel to "The Beast Below," as this story portrays a later point in humanity's quest to settle on other planets.
Episode 3: 'Thin Ice'
- There really was an elephant brought onto the ice during the last great Frost Fair in 1814.
- The Doctor has visited the last Frost Fair before. In the episode "A Good Man Goes To War," River Song tells Rory that The Doctor had just taken her ice skating on the Thames to celebrate her birthday.
- In script for a scene deleted from the episode, The Doctor tells Bill that he had spent his last visit to the Frost Fair trying to get a piano on to the ice so Stevie Wonder could perform for his wife. This performance was also mentioned by River in "A Good Man Goes To War."
- In one scene transition, there is a brief shot of a couple skating, though only their feet are seen. As this takes place almost immediately after where the aforementioned deleted scene would have taken place, this couple may be The Eleventh Doctor and River.
- The story The Doctor tells the orphans is "The Tale of The Thumb-Sucker," which ends with a boy having his thumbs cut off by a man with a giant pair of scissors.
- The Fish-Creature, chained and kept in the service of humans, is in a similar predicament to the space whale in "The Beast Below."
- The Doctor leaving the fate of the creature to Bill is similar to the final act of "Kill The Moon," in which he leaves the fate of the infant creature about to hatch from the moon in the hands of Clara and the rest of humanity. Bill seems to handle the scenario much better than Clara did.
Episode 4: 'Knock Knock'
- The house that Bill and her friends move into was previously used as a filming location for "Blink," the first episode to feature the now iconic Weeping Angels.
- In a deleted scene, one of Bill's roommates (Harry) would have been revealed as the grandson of Fourth Doctor companion Harry Sullivan. The scene was cut due to the belief that modern #Whovians wouldn't get the reference.
- At one point, Bill refers to The Doctor as "grandfather." This is what Susan called him during the First Doctor era.
- Except for scanning the Dryads, The Doctor's Sonic Screwdriver is used very little in this episode. The house is old and mostly made of wood, a material that the Sonic is entirely ineffective against.
- Bill's friend Shireen cries "I'm a celebrity, get me out of here!" Sixth Doctor Colin Baker was once a contestant on that show.
- David Suchet, who guest starred as the Landlord, accepted the part without ever reading the script.
- When watched with headphones or surround sound, "Knock Knock" becomes an immersive 4D experience. The episode uses binaural beats in its soundtrack, making it seem as if the knocks and creaks are happening all around you.
- Whoever is inside the Vault plays "Fur Elise" on the piano, followed by "Pop Goes The Weasel."
Episode 5: 'Oxygen'
- At first glance, the oxygen gauge on the spacesuits strongly resembles the neural relay seen on the suits of River and her team in "Silence In The Library"/"Forest Of The Dead."
- The concept of the human remains staying inside the spacesuits while they move on their own is also similar to events in the above episodes. However, the spacesuits were being moved by the Vashta Nerada rather than entirely on their own, and only the human skeletons remained.
- This is the first time the Twelfth Doctor breaks his Sonic Screwdriver. Both the Tenth and Eleventh Doctors have broken them previously.
- Bill's statement to Dahh-Ren about facing racism herself is a throwback to her terrible treatment by Sutcliffe in "Thin Ice," two episodes earlier.
- A shot of The Doctor (while blind) was seen back in the promo reel after "Return Of Doctor Mysterio." However, the cloudy digital effect had not yet been added to his eyes.
- Peter Caulfield, Kieran Bew and Mimi Ndiweni, who played Dahh-Ren, Ivan and Abby, have previously voiced characters in Big Finish's Bernice Summerfield audio stories.
Episode 6: Extremis
- The Doctor uses his Sonic Sunglasses, introduced in Series 9, to hide the fact that he has gone blind.
- Joseph Long, the actor playing The Pope, has previously appeared in Doctor Who as Rocco Colasanto, the head of a friendly Italian family who briefly live with Donna Noble in the alternate reality of 'Turn Left', before being shipped off to a Labor camp.
- The Doctor unintentionally ruins Bill's date by letting the Pope wander into her Bedroom. This is sadly not the first time something like this has happened, as The Doctor also interrupted Clara's first date with Danny Pink.
- Bill's comment that moving out didn't work out for her is a throwback to the events of 'Knock Knock'.
- Missy comments that The Doctor had retired to 'Domestic bliss on Darillium'. This is a reference to the 24 years he spent there saying goodbye to River Song.
- It is revealed that River Song sent Nardole to watch over The Doctor. Probably because, as multiple previous companions have told him, The Doctor should not be alone.
- Nardole seems to be the current keeper of River Song's diary, presumably recovering it from The Library.
- A comment is made about Time Lords suffering 'relapses of life'. Missy/The Master has returned to life after an execution before, in Doctor Who: The Movie.
- Missy once again asserts that she is The Doctor's friend. Her plot involving the Cybermen back in 'Dark Water'/'Death In Heaven' was the result of a misguided attempt to get her friend back.
- Current show runner Steven Moffat has long discussed including a 'stealth two-parter', where viewers do not know a story is a two-parter until the first episode ends. He has finally succeeded, with the events of this episode leading into the next, 'The Pyramid At The End of The World'.
Episode 7: 'The Pyramid At The End Of The World'
- The Doctor is seen playing his guitar once again. The guitar has become a signature item for the Twelfth Doctor.
- While playing his guitar inside the Tardis, The Doctor claims that he is meditating. This is likely a reference to the episode 'The Magician's Apprentice' and its prologue minisode, 'The Doctor's Meditation'.
- The Doctor is called upon to assume his responsibilities as President of Earth for the third time. The first two such occasions occurred in 'Death In Heaven' and the two-part episode 'The Zygon Invasion '/'The Zygon Inversion'.
- Bill states that the current President is orange. This is an obvious jab at #DonaldTrump.
- The Monk's Pyramid is situated in Turmezistan. The rebel Zygons had a training facility there in 'The Zygon Inversion'.
- The scientist, Douglas, is struggling after a big night out. A brief shot of his computer screen reveals an email from 'P.Hilton', a possible reference to socialite Paris Hilton.
- Jaime Hill, the actor perfroming as the head Monk, has previously appeared as one of The Silence, and The Foretold in 'Mummy On The Orient Express'. He also appeared on stage as a Silent at the 2013 'Doctor Who At The Proms' presentation.
- Tim Bentinck, the voice of the Monk, has performed in a number of Doctor Who audio stories for Big Finish.
- At eight words, 'The Pyramid At The End Of The World' clocks up the biggest word-count of any Doctor Who episode title.
Episode 8: 'The Lie Of The Land'
- The flickering 'Truth' symbol throughout the episode offers an early hint to its ultimate resolution. Bill is the carrier of the Monks illusion, but since she does not believe in it, it is not as strong as the monks would hope, hence the flickering.
- Footage from 'Blink', 'Nightmare In Silver', and 'The Pilot' is used in the episode, edited to include The Monks.
- Bill and others gathered around a Magpie Electricals store to watch The Doctor's broadcast. A Magpie Electrical store was the centre of the action in 'The Idiot's Lantern', and another was seen in the background during 'The Beast Below'.
- One of the Monk's statues is seen in Sydney, Australia, where Bill and The Doctor briefly visited in 'The Pilot'.
- Missy plays 'Gnossiene No.1' And 'The Entertainer' on her Piano.
- Missy is again unconcerned about the fate of The Doctor's companion. She previously put Clara in danger multiple times throughout 'The Magician's Apprentice'/ 'The Witch's Familiar'.
- The Tarovian Neck Pinch that Nardole used on the soldier is similar to a technique used by First Doctor companion Ian Chesterton in 'The Aztecs'.
- The heater in The Vault was brought in to keep the actors warm during filming. The Director liked it, keeping it in the shot for the episode's final scene.
- This is one of only nine Doctor Who stories in which the Tardis does not appear.
Episode 9: Empress Of Mars
- This episode is a sequel to the Second Doctor episodes 'The Ice Warriors' and 'The Seeds Of Death'.
- It is a prequel to the two 'Peladon' stories, which took place during the third Doctor's tenure.
- This marks the first mention of the Galactic Federation in the revival series.
- The Idea of Ice Warrior hives has been mentioned before. The Doctor promised to take Clara to one in 'Robots of Sherwood'.
- Nigel Catchlove was named after a real life soldier with the same surname. He was played by Ferdinand Kingsley, the son of Sir Ben Kingsley.
- The portrait of Queen Victoria kept by the Soldiers is painted in the likeness of Pauline Collins, who played her in 'Tooth And Claw'.
- Iraxxa tells her Warriors to "Sleep No More!". This was the title of the last episode written by this episode's writer, Mark Gatiss.
- Alpha Centauri is voiced by Ysanne Churchman, the same actress who voiced the character in the classic series.
- This is the second Ice Warrior episode written by Mark Gatiss. The first was Series 7's 'Cold War'.
Episode 10: 'The Eaters Of Light'
- The episode was written by Rona Munro, writer of the final classic Who story, 'Survival'. It was her first TV script in 28 years.
- Bill realizing that the Tardis translates languages for her is similar to Donna Noble making the same discovery while speaking Celtic in 'The Fires Of Pompeii'.
- Nardole is seen telling the Scots a story about an adventure aboard the Marie Celeste, a real life ship whose crew mysteriously disappeared. A sign belonging to the ship was displayed near the vault in 'The Pilot'.
- Nardole claims to know 10% of The Doctor's secrets. He has likely gathered said secrets from River Song's diary, which he was seen to possess in 'Extremis'.
- In the episode's climax, Scottish girl Kar heads into the portal to fend off the Eater Of Light, accompanied by Centurion Lucius and the rest of the Ninth Legion of the Roman army. Eleventh Doctor companion Amy Pond was Scottish, while her eventual husband, Rory, once protected her in the guise of a Roman centurion.
Episode 11: 'World Enough And Time'
- 'World Enough And Time' is the first televised story to feature more than one incarnation of #TheMaster.
- The episode gives the third possible origin of the Mondasian Cybermen. Alternative origin stories were seen in the Comic 'The Cybermen' and the popular audio story 'Spare Parts'.
- The Master's use of a disguise for most of the episode is a throwback to the classic era of Doctor Who, where The Master disguised himself often.
- The Doctor knocks out Jorj using Venusian Aikido. This was a fighting style often used by the Third Doctor.
- Missy claims that The Doctor's real name is actually Doctor Who. This joke has been used before, such as when The Second Doctor signs a note as 'Doctor. W'.
- This is not the first time that The Doctor has had to rescue a companion from a faster-moving time stream. That was in 'The Girl Who Waited', where The Eleventh Doctor and Rory must rescue Amy from the Two Streams quarantine facility.
- Bill is the first companion to be converted into a Mondasian Cyberman. Other associates of The Doctor, such as Danny Pink and an alternate universe Jackie Tyler, have been converted into other varieties of Cybermen.
Episode 12: 'The Doctor Falls'
- The shot of Cyber-Bill carrying the unconscious Doctor is similar to a now iconic shot of The Eleventh Doctor carrying Amy in 'Asylum Of The Daleks'.
- Missy stating "I know you've fallen" while discussing The Doctor's many deaths is a reference to The Master being responsible for the Fourth Doctor's death by causing him to fall from a tower in 'Logopolis'
- The Doctor offers a child a jelly baby, another clear reference to The Fourth Doctor.
- Bill is the third major character to resist Cyber-programming for an extended period of time. The first two were Danny Pink and Brigadier Lethbridge-Stewart in 'Death In Heaven'.
- "Without Hope, without witness, without reward", said by The Doctor as he prepares to enact his plan, has been a recurring quote this series, first seen in River Song's diary, then repeated by both Missy and The Doctor before her halted execution.
- While attempting to hold off his regeneration, The Twelfth Doctor repeats the final words of his two previous incarnations.
- The First Doctor is wearing the same outfit he wore in 'The Tenth Planet', his final televised story.
There will be more Easter Eggs to come as the episodes air.