"Bad Wolf" is an episode so heavily steeped in references to British TV and classic Doctor Who it would take a list twice as long as this one to get everything in, and even then there would still be tiny moments that could bear further exploration, depending where you're from and how much you can infer from context.
Suffice to say that this is the story in which British TV stars Anne Robinson, Davina McCall, Trinny Woodall and Susannah Constantine become robots and try to kill our three heroes, while the Doctor is once again faced with the consequences of his own actions.
The original title for the episode was "Gameshow World" (or possibly "Gameshow World!", the first Doctor Who episode to contain an exclamation point), which was changed when Russell T Davies decided to complete the Bad Wolf story arc he had been so carefully seeding throughout the whole of the series.
He had wanted to make a spoof of reality TV as far back as 2000, when he first began pitching a new series of Doctor Who to the BBC. The idea for the Anne Robinson robot Anne Droid came to him when he was promoting his series Queer as Folk in New York and spotted the real Anne Robinson's face glaring down from a huge screen in Times Square. As no one in the production team was sure she'd agree to send herself up, a celebrity impressionist was booked to play the part, but thankfully Robinson accepted.
Meanwhile, the Big Brother house (complete with theme tune by Paul Oakenfold) is run by the Davinadroid, voiced by the real Davina McCall, presenter of the British show. Her catchphrases, well known to viewers, are replicated here, including the warning "You are live on channel forty four thousand [normally Channel 4], please do not swear" and "I'm coming to get you," when a housemate is evicted.
As the Doctor, Jack and Lynda are caught by security, they are told, "You will be taken from this place to the Lunar Penal Colony, there to be held without trial." Had they been sent there, it would have been a return trip for the Doctor, as his Third incarnation was sent there during the 1973 adventure "Frontier in Space," as a Draconian spy.
One of the questions the Anne Droid asks is where the foodstuff gaffabaque comes from. This is a nod to fans, as the correct answer is the planet Lucifer, home to a race called Angels (not those Angels) who met the Seventh Doctor in the novel "Lucifer Rising," which was released in 1993. Her questions also contain the first mention of the word Torchwood in Doctor Who.
On a similar moment of arcane Whovian trivia, the question Rose answers concerning the Face of Boe states that he is the oldest inhabitant of "the Isop Galaxy." This constellation also contains the planet Vorbis, as visited by the First Doctor in "The Web Planet."
The Doctor's amnesia suddenly disappears when he's in the Big Brother house, and he remembers visiting Kyoto in 1336 with Rose and Jack, and them only just getting away with their lives. Although this adventure is unrecorded in Doctor Who's various media, it is most likely to have been during the historical period between Ashikaga Takauji's first attempt to take over the city in February of that year (he only managed a few days before being ousted) and his second, more successful invasion in May.
In a moment of life meeting art, the orange chair used in the diary room scene was eventually sold to Channel 4, and they used it in their show Ultimate Big Brother as a diary room chair. Thankfully no one was disintegrated upon leaving.
Composer Murray Gold created a musical score for the moment when the Dalek fleet is first shown, which includes a choir singing "Mah Kor'ei." This, according to the DVD commentary for this episode, is Hebrew for "What is happening?"
When Captain Jack asks what the defabricator is, shortly before it disintegrates his clothes, he then quips, "OK, defabricator—does exactly what it says on the tin." This is a reference to a series of British TV commercials for Ronseal paints and varnishes.
The term very quickly entered common usage in British English, as a quick way of saying that something is exactly what it appears to be.
Oh, and John Barrowman likes to claim there was a version of that scene filmed in which you could see his naked rear end. It was never broadcast.
Now read the rest of the 10 Things You May Not Know About Doctor Who archive.