Knock Knock (TV story)

 was the fourth episode of the tenth series of Doctor Who produced by BBC Wales.

Synopsis
Bill and her friends rent an old house to live in, but the floorboards and the walls are creaking, and there's a creepy Landlord lurking around. Can the Doctor save the day as creatures come crawling out of the wood?

Plot
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Cast

 * The Doctor - Peter Capaldi
 * Bill - Pearl Mackie
 * Nardole - Matt Lucas
 * The Landlord - David Suchet
 * Eliza - Mariah Gale
 * Shireen - Mandeep Dhillon
 * Felicity - Alice Hewkin
 * Paul - Ben Presley
 * Harry - Colin Ryan
 * Pavel - Bart Suakvek
 * Estate agent - Sam Benjamin
 * Young Landlord - Tate Pitchie-Cooper

Crew
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Culture

 * The figure behind the Vault can play the piano.

Technology
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Science
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Species

 * Time Lords need to sleep after regeneration.
 * The Doctor calls the woodlice Dryads, though he later reverts to just calling them lice.

Foods and beverages
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People

 * Asking the Landlord who is the Prime Minister, the Doctor lists Margaret Thatcher, Harriet Jones, Harold Wilson and Anthony Eden as candidates.
 * The Doctor once sat in on a recording session for Quincy Jones when the bass player (who couldn't play anyway) was revealed to be an alien.

The Doctor

 * The Doctor offhandedly mentions regeneration to Bill; he avoids elaborating on it.

TARDIS
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Locations

 * The Doctor mentions the Deathtrees of Souta Four and the Carnivorous Forest on Enflusis when questioning as to where the Dryads might have originated.

Music

 * The figure behind the Vault plays Für Elise by Beethoven and Pop Goes The Weasel, a famous nursury rhyme, on a piano.

Story notes

 * David Suchet said in The Fan Show Aftershow that he used a real life experience of being covered in woodlice for the scene where the Dryads come crawling all over the Landlord.
 * An an interview in Doctor Who Magazine #512, writer Mike Bartlett indicated that the Harry was intended to be the grandson of Fourth Doctor companion Harry Sullivan, but the reference was cut.

Ratings
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Filming locations
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Production errors
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Continuity

 * The Doctor mentions Prime Minister Harriet Jones, who ascended after aiding his ninth incarnation in defeating the Slitheen. (TV: Aliens of London/World War Three) His tenth incarnation, however, would set in motion her deposition after she ordered the destruction of the retreating Sycorax. (TV: The Christmas Invasion) She would help save the world one final time against the Daleks. (TV: The Stolen Earth)
 * The TARDIS materialises around Bill's possessions. It had done so previously around passengers. (TV: The Parting of the Ways, Blink, The Runaway Bride, Dinosaurs on a Spaceship, Hell Bent)
 * The Doctor remarks on the Time Lords' dress sense, having done so earlier in his life. (TV: Time Crash, Journey to the Centre of the TARDIS, Nightmare in Silver, Hell Bent)
 * The Doctor reveals he's a Time Lord. (TV: The War Games et al., Doctor Who, The End of the World et al.)
 * The Doctor mentions regeneration, but glosses over it, similar to how his tenth incarnation did such with Martha Jones in regards to his race. (TV: Gridlock)
 * The Doctor had previously faced creatures who absorbed people into walls. (TV: Flatline)
 * Bill introduces the Doctor as her grandfather. The Doctor once travelled with his granddaughter Susan Foreman, who called him grandfather. (TV: An Unearthly Child - The Dalek Invasion of Earth, The Five Doctors)
 * Bill's sexuality is mentioned as she informs a male flatmate, after he makes overtures, that he isn't her type and she prefers girls. (TV: The Pilot)
 * Bill puts a picture of her mother, which was taken by the Doctor, on the wall. (TV: The Pilot)
 * One of the flat mates theorise dolls could be creeping around upstairs. The Doctor encountered a house of dolls in his eleventh incarnation. (TV: Night Terrors)
 * The Vault is tended to by Nardole once more, the Doctor revealing a piano is inside. (TV: The Pilot, Thin Ice)
 * In an attempt to convince herself that there's nothing strange about the house, Bill remarks that "There's no living puddles or weird robots, big fish..." (TV: The Pilot, Smile, Thin Ice)
 * The Doctor claims sleep is for tortoises, (TV: The Talons of Weng-Chiang) as he doesn't sleep much himself. (TV: Good Night)

DVD releases
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Blu-ray releases
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Digital releases
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