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

 * Bill makes reference to Indiana Jones.
 * Shireen says "I'm a celebrity, get me out of here", a reference to the reality TV series. She also refers to the building as a "freaky Scooby Doo house".

Music

 * The figure behind the Vault can play the piano.
 * Pavel has a vinyl record, DVD players and speakers.
 * Bill has a whole playlist for Little Mix on her phone. The playlist includes the song Black Magic.
 * One of the tenants from 1977 owned the David Bowie album Heroes.
 * Pavel has Back: Sonata #1 by Itzhak Perlman playing in G Minor for Solo Violin, BWV 1001 - 1. Adagio.
 * The figure behind the Vault plays Für Elise by Beethoven and Pop Goes The Weasel, a famous nursery rhyme, on a piano.

Locations

 * When Felicity bemoans lack of phone reception, Shireen says she needed a landline and Felicity jokingly asks "What is this, Scotland?".
 * The Doctor mentions the Deathtrees of Souta Four and the Carnivorous Forest on Enflusis when questioning as to where the Dryads might have originated.

Businesses

 * A shop named The Fabric Mill is seen.

Technology

 * The house has no washing machines.
 * The plugs can't take the students' phones.
 * The house has an old-fashioned television set.
 * Pavel plays a vinyl record using a USB turntable (even though it is not shown to be connected to a computer).
 * The Doctor uses the sonic screwdriver as a light source.
 * Eliza has a music box.
 * There's a typewriter in the basement.

Science

 * The Doctor finds an oil burning heater.

Species

 * The creepy, creaky house has skulls from gazelles hanging on the walls.
 * Paul and Shireen jokes to Felicity that the house possibly has a "doll, that's come to life" or a "massive, freaky spider", to which Bill says it's probably just a mouse, and Felicity indirectly says she has a fear of mice.
 * Bill ask if there's a cat in the house. The Landlord denies this.
 * 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

 * The house has a picture of a bowl of pears.
 * There's a book on Farmhouse Cooking in the kitchen.
 * The students eat Chinese. The Doctor loves Chinese.
 * The Doctor (noisily) eats a krupuk.

People

 * Bill has a teddy bear.
 * Harry's relatives got arrested for trying to steal a bit of the Great Wall of China.
 * Bill hangs up a photo of her mum.
 * Asking the Landlord who is the Prime Minister, the Doctor lists Margaret Thatcher, Harriet Jones, Harold Wilson and Anthony Eden as candidates.
 * The Landlord has a tuning fork.
 * 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.
 * Felicity is Musophobic and Claustrophobic.
 * Felicity tried to call the police.
 * Shireen wanted to call an ambulance.
 * A tenancy agreement from 2 September 1997 was signed by Jake Christie, Annie Wren, Jonathan Frost, Sarah Tiller, Margaret Opthorn and Carl Richards. There is a further agreement from April and signed in May 1977 and one from 1957.

Organisations

 * Bill and her friends go to Redcliffe Lettings to find a new house to live in.
 * Redcliffe Lettings' phone number is 01174 960313.

The Doctor

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

TARDIS
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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.
 * In an interview for Doctor Who Magazine #512, writer Mike Bartlett indicated that Harry was intended to be the grandson of Fourth Doctor companion Harry Sullivan, but the reference was cut. A possible remnant of this has Harry recognising the Doctor's name and calling him a legend, despite the episode establishing that Bill is not yet closely acquainted with her new flatmates.
 * Weird People by Little Mix is playing extra-diegetically in the scenes where Bill and her friends are looking for a new house.
 * Shireen refers to 11 Cardinal Road as "a freaky Scooby Doo house". The episode was partly filmed on location on the same property used for Wester Drumlins in TV: Blink - in which a character also referred to the place as "Scooby Doo's House".

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 says he loves Chinese. (TV: The Power of Three)
 * Bill says there are bits of her life that the Doctor is not in. Amy Pond and Rory Williams used to have a double-life, (TV: The Power of Three) and so did Clara Oswald. (TV: The Day of the Doctor)
 * When Bill says they should get the Doctor, Shireen asks if he's gonna give a lecture. (TV: The Pilot)
 * 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.)
 * Regeneration is mentioned. (TV: The Tenth Planet/The Power of the Daleks, The War Games, Planet of the Spiders/Robot, Logopolis/Castrovalva, Destiny of the Daleks, The Caves of Androzani, Time and the Rani, Doctor Who, The Night of the Doctor, The Day of the Doctor, The Parting of the Ways, Utopia, The Stolen Earth/Journey's End, The End of Time, Day of the Moon, Let's Kill Hitler, The Time of the Doctor, Hell Bent)
 * 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)
 * The Doctor takes offence at being described as Bill's grandfather, suggesting father be more accurate given his appearance. (TV: The Caretaker)
 * Bill's sexuality is mentioned as she informs Paul, after he makes romantic 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 Doctor uses the sonic screwdriver as a light source. (TV: Thin Ice)
 * The Doctor has met people made of wood before. (TV: The End of the World, The Doctor, the Widow and the Wardrobe)
 * 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) usually only after regeneration (TV: Spearhead from Space, Robot, Castrovalva, Time and the Rani, The Christmas Invasion, Deep Breath) or after a big lunch. (TV: The Two Doctors)
 * The Doctor refuses to "high-five" Harry (TV: Under the Lake, Time Crash ).

DVD releases
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Blu-ray releases
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Digital releases
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