"Planet of the Dead" is not only the last of the Tenth Doctor's "fun" stories, as he heads into self-doubt and recrimination prior to his forthcoming regeneration, it also features a loving recycling of one of Doctor Who's signature visual tricks. It takes an iconic object, familiar primarily (but not exclusively) to British viewers and places it in an alien context.

The TARDIS is one example, as is the Titanic in "Voyage of the Damned" and now the iconic London double-decker bus has made a trip across the galaxy too.

Here are a few other things to keep an eye out for, the next time you watch:

(The episode is available on Amazon and iTunes.)

"Planet of the Dead" is the first Doctor Who story to have been created by two writers since the series was relaunched. Russell T Davies brought in his The Sarah Jane Adventures co-writer Gareth Roberts and set him to work adapting two themes from his The New Doctor Who Adventures novel The Highest Science. One was a battle between humanity and the Chelonians, a race of aggressive turtle-ish aliens — and the other was a commuter train that had been hijacked and transported to another planet. In the end, the latter idea was deemed strong enough to hang the whole story on.

Another idea in the mix was that the TARDIS might appear in the middle of a giant space dogfight, or that the train (now a London double-decker bus with the Doctor on board) might vanish through a wormhole and appear in the middle of a giant space dogfight.

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

There had also been a longstanding plan to work with the production team of Star Trek: Enterprise on a crossover story, which was stymied by the cancellation of that series in 2005. Russell T Davies considered going ahead with the story anyway, having the Doctor appear on a spaceship called "Endeavor" and affectionately mocking the Star Trek universe, but he dropped the idea as being unsuitable for one of the stories leading to the Tenth Doctor's grand finale.

There are two references to the Fourth Doctor's first adventure, "Robot," in this story. First the Doctor asks Malcolm if his favorite UNIT file was "the giant robot," before focusing fully on the job in hand. Then later on, Captain Magambo says, "I don't believe it. Guns that work" when UNIT soldier realize they can actually shoot down an alien menace for once. This echoes a thought expressed by the Brigadier: "You know, just once I'd like to meet an alien menace that wasn't immune to bullets."

Having spent the six months before filming playing Hamlet in Stratford-Upon-Avon for the Royal Shakespeare Company, the naturally Scottish David Tennant was concerned that he might have spoiled his English accent to play the Doctor. Filmed for the first readthrough of the script, he explained that Hamlet's accent was English but "more posh," and that he'd have to watch some previous episodes of Doctor Who to get the voice right.

Adam James, who played the unlucky detective Macmillan, is an old friend of David Tennant's. He is also the godson of Third Doctor Jon Pertwee.

Continuing Season Four's grand tradition of bringing in a comedian for a cameo appearance, Lee Evans plays Professor Malcolm Taylor, a character designed to subtly undermine the stern demeanor of Captain Erisa Magambo. It was only after the episode had been written that Gareth Roberts noted Malcolm Taylor was also there to represent Doctor Who fandom to the Tenth Doctor, in much the same way that Osgood later would for the Twelfth.

https://www.youtube.com/watch?v=SmrreflioZ4

Malcolm Taylor names a unit of measurement a "Bernard" in tribute to Professor Bernard Quatermass, but it's not clear whether he's invoking the name of the professor in tribute to the classic science fiction TV series The Quatermass Experiment, written by Nigel Kneale, or if Bernard Quatermass actually exists in the Doctor Who universe as a real person. There was some crossover, in that the British Rocket Group, for whom Quatermass works, exists in "Remembrance of the Daleks", but he's never explicitly named as a real person. For his part, Nigel Kneale was not a Doctor Who fan, and even turned down the chance to write for the show, because (according to the Telegraph) "his children were growing up and he did not want them exposed to anything so nasty."

There's an advert on the side of the bus for Neon by Naismith, which is a nod to the phone company owned by billionaire Joshua Naismith, who will later appear in "The End of Time."

https://www.youtube.com/watch?v=bxFjg0eI6-U

The Doctor Who production team bought two buses for the shoot, but one was damaged in transit to the location shoot in Dubai. The production team looked over the damage and decided to incorporate it into the story rather than send for the spare bus, which was still in Cardiff, and have to find a third one for filming in the UK. So they made a feature of the damage, adding smoke and lights to make it more dramatic, then attacked the spare bus so that both vehicles matched.

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