"Boom Town" is the story of the Doctor consolidating everything that has happened to him since he first met Rose Tyler. In that time, he's learned to let go of some of his bitterness over the Time War, he's dropped his defenses enough to want to show Rose how exciting the universe can be, and in turn, she's shown him that, despite feeling hurt and guilty and lost, he doesn't have to be alone.

It also features a return visit from Mickey Smith, Captain Jack repairing the TARDIS like an expert, and a repeat confrontation with one of the family Slitheen.

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.)

This is one of the few stories in Season 1 that hadn't been part of Russell T Davies' original pitch for the reborn Doctor Who. The TV writer Paul Abbott (Shameless, State of Play) had been approached for a script, but had to pull out due to having other commitments, so Russell chose to revisit the character of Blon Fel-Fotch Passimeer-Day-Slitheen from "Aliens of London" / "World War Three".

Paul Abbott's proposed story was titled "The Void," would have been set in Pompeii in A.D. 79 (hence the reference to "volcano time" in the previous story "The Doctor Dances") and would have contained the startling revelation that Rose Tyler's life had been artificially manipulated by the Doctor so that she would develop all the qualities of a perfect companion.

The Doctor has had to describe the TARDIS's unique shape plenty of times over the years, and in the classic series, the phrase that he would most commonly reach for is "chameleon circuit." However, when Rose explains it to Mickey, she uses the term "cloaking device," which comes from Star Trek. If that seems like a strange cross-fandom moment, consider that Rose is far more likely to have seen Star Trek than Doctor Who.

https://www.youtube.com/watch?v=VLZOFZggG4w

The Cardiff square in which the TARDIS lands, the place with all the rift energy in front of the Wales Millennium Centre, is named Roald Dahl Plass after the author Roald Dahl, who was born in Cardiff in 1916.

As the new Doctor Who is a Welsh production, based in Cardiff, this story was a chance to show off a few local landmarks in the way London stories always show Big Ben. However, those scenes in which Rose and Mickey argue in front of the water tower at Roald Dahl Plass had to be spread across two separate night shoots, as the fountain automatically switches off if temperatures drop below a certain level (which they did).

Other particularly Welsh references in the story include the dig from Blon at the problems of a bilingual culture ("it wasn't my fault that 'Danger: Explosives' was only written in Welsh!"); the Cardiff police cars with "Heddlu" written on them; the fact that the nuclear power station is to be named "Blaidd Drwg" ("Bad Wolf"); and this moment of cultural paranoia, familiar to anyone who grew up in a small town: "We're in Cardiff. London doesn't care! The South Wales coast could fall into the sea and they wouldn't notice... Oh... I sound like a Welshman. God help me, I've gone native."

As is now becoming traditional within the reborn Who, Rose drops a reference to the star system Justicia as a tip of the hat to something that happens in another Doctor Who media, bringing it into the canon of the TV show. In this case, it's the Doctor Who New Series Adventures novel The Monsters Inside by Stephen Cole, featuring the Ninth Doctor and Rose. Justicia, located near the edge of the Mutter's Spiral, is a prison comprising three suns and six planets: Justice Alpha, Justice Beta, Justice Gamma, Justice Delta, Justice Epsilon and Justice Prime.

On a similarly bookish note, Blon claims that she was forced to grow up a murderer: "I was made to carry out my first kill at 13. If I'd refused, my father would have fed me to the Venom Grubs."

This may well be a reference to the small creatures known as Zarbi larvae, from the First Doctor adventure "The Web Planet." In the novelization of this story—the only way to experience it for those Whovians who were too young to watch at the time—these living weapons, who could shoot jets of venom at their intended prey, were also called Venom Grubs.

https://www.youtube.com/watch?v=nLi6KmoFTX4

Another tip of the hat to the past occurs when Jack examines the machine/surfboard upon which Blon intends to make her escape, squealing, "Is that a tribophysical waveform macro-kinetic extrapolator?"

Tribophysics is a Gallifreyan science dealing with surfaces in relative motion that interact. It was first mentioned in the Fourth Doctor serial "The Pyramids of Mars" when the Doctor opens a door just by moving his hand. Sarah Jane Smith (also) squeals, "Tribophysics!" to which the Doctor replies, "Yes."

William Thomas deserves a special mention at this point. He plays Mr. Cleaver, who first flags up the problem with the design of Blon's nuclear power station (and lives to regret it), has a very special place in Doctor Who history. He had already played a character called Martin in the Seventh Doctor story "Remembrance of the Daleks," making him the first actor to appear in both old and new Who. He later went on to play Gwen Cooper's father, Geraint, in Torchwood.

NEXT: 10 Things You May Not Know About ‘Bad Wolf’

Now read the rest of the 10 Things You May Not Know About Doctor Who archive.