"The End of the World" is the story that cemented the return of Doctor Who, building on the strong chemistry between Rose Tyler and her new friend the Doctor, who could no longer get away with answering "Because I'm an alien" to every question. It also showed the Doctor in a crueller light than in the previous episode "Rose," allowing this teenage runaway to begin to understand the man in whose time machine she had stowed away.

Here are a few things that you should keep an eye out for, the next time you watch. (The episode is available on iTunes and Amazon.)

It was the second story in the new series, the one in which the Doctor shows Rose what it is like when he travels away from present-day Earth. So it was important that the special effects were top-notch, as indeed they are. However, most of the SFX budget for the entire series was spent on this one episode, with Cassandra, the sun expanding, the earth being destroyed and everything else.

https://youtu.be/yjrJEi0n4J0

It paid off though, as it was after this episode aired that the Christmas special and second series were commissioned.

The set up of the story is that a group of the rich elite has gathered to watch the demise of the planet Earth, as if it were a civic event. It's a slight twist on a similar premise in Douglas Adams' The Hitchhikers Guide to the Galaxy, in which a Vegas-style restaurant has been set up in which you can watch the end of the universe as if it was an after-dinner show.

Early on, Rose expresses outrage that the TARDIS telepathic translation circuits are monitoring her brain. This is a reference from classic Doctor Who (as well as a convenient way to allow races from all over the universe to communicate with the Doctor and his companions without the need for space translators), specifically a conversation between the Fourth Doctor and Sarah Jane Smith in "The Masque Of Mandragora" in which she asked how it is that she could speak Italian and he said it's "a Time Lord gift I allow you to share." Sarah didn't seem to mind the interference, but then she'd already been an old hand at Time Lords by then. Rose has only just met this man, and his blue box is already poking around inside her head.

The Doctor and Rose have a bit of banter over the term jiggery-pokery. (Doctor: "I came first in jiggery-pokery, how about you?" Rose: "Nah, failed hullabaloo.") This is a term that dates back to the Scottish word jouk, meaning "to swerve out of the way of an incoming blow." Joukery became a word for dealing with things—particularly business transactions—in a non-straightforward or underhanded fashion, while pawk is a Scots slang term for a prank or jape. Joukery-pawkery became, therefore, a term for confidence tricks or scams. By the time the Doctor got his hands on the term, it just meant broadly the same as malarkey.

The Doctor makes a speech about humans that contains references to three prominent news stories concerning public health that will have been familiar to British viewers: "You lot. You spend all your time thinking about dying. Like you're going to get killed by eggs or beef or global warming or asteroids. But you never take time to imagine the impossible. Maybe you survive."

The beef mentioned is a reference to the scare over bovine spongiform encephalopathy (more commonly known as mad cow disease); we all know about global warming; and when the Doctor mentions eggs, he's talking about a U.K. scare over salmonella in eggs that dominated the news media in the late 1980s, after the minister Edwina Currie said most British eggs were infected, causing a panic-driven slump in egg sales. She later resigned over her role in the affair.

Russell T Davies was inspired to create the vain and shallow (in both senses of the word) Cassandra after watching the Academy Awards and worrying about the health of the actresses on the red carpet. He told the Sunday Mirror: "It was horrific seeing those beautiful women reduced to sticks. Nicole Kidman struck me in particular. Nicole is one of the most beautiful women in the world. But she looks horrifying because she's so thin. It's like we're killing these women in public. We watch while you die."

Russell's original script mentions Cassandra having collected various treasures from human history in cabinets, including the Magna Carta and a first edition of Harry Potter and the Philosopher's Stone (according to the book Doctor Who: The Shooting Scripts). This would have brought forward J.K. Rowling's first mention in Doctor Who by almost exactly two years, as she was later namechecked in "The Shakespeare Code." Russell had also asked her to write a script for Doctor Who in 2005, but she was too busy.

Speaking of the Face of Boe, he wasn't intended to be a recurring character at first, otherwise his name may have been different, as it is thought to have been a playful nod to the Rudyard Kipling poem "The Ballad of Boh Da Thone," in which a despotic and legendary soldier is beheaded.

Rose mentions having seen something about the end of the Earth on Newsround Extra. Newsround is a long-standing current affairs TV bulletin for BBC1 and CBBC aimed at children. Newsround Extra is the extended version of the show that covers a bigger topic that is in the news at the time. With pleasing neatness, there was a reporter for Newsround Extra at the shoot for this episode, and here is his on-set report.

Several elements that we now think of as being integral to Doctor Who made their debut appearances in this story. There's the (slightly) psychic paper, the Face of Boe, the revelation that Gallifrey has been blown up in the Time War and the fact that the Doctor is the last of his kind. Then there's the reference by the Moxx of Balhoon to "the Bad Wolf scenario," which sets up the story arc for all of the rest of Season One.

And of course it's only when the Doctor opens up to Rose that she really begins to trust him:

https://www.youtube.com/watch?v=cXdRts6kJC0

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