"Kill the Moon" takes one of classic Doctor Who's most potent settings — a base in a hostile unearthly terrain, sometimes with insects — and introduces a steadily-escalating note of tension between the cocksure Time Lord and his frustrated companion.

It also finishes with a note of magic realism (spoilers!) that is so strange it would be totally impossible to fit credibly into any science fiction show that hasn't already managed to cram a time and space machine into a telephone box.

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

(The episode is available on iTunes and Amazon.)

The script was originally written for Matt Smith's Doctor. Peter Harness, who wrote it, was instructed by Steven Moffat to make the first half exceptionally scary, in fact, to "Hinchcliffe the s*** out of it," referring to former Who producer Philip Hinchcliffe, who is widely beloved by fans of classic Doctor Who for delivering a particularly scary run of stories between 1974 and 1977.

Not that Peter needed telling twice, as he told Cultbox: "I've found myself going back to my first memories of those first few Whos I saw, trying to excavate what had the biggest effect on me as a child, and trying to play on those things when writing.

“I certainly didn’t worry about making it too scary. I remember Doctor Who as being scary, and I think it’s at its best when it is. Much of the best children’s literature is scary, and I think as far as Doctor Who is concerned, it often comes down to the nearly fifty-year-old question of whether it's too scary for adults."

Some of the lunar shots were filmed in Lanzarote, one of the Canary Islands, this was Doctor Who's second visit there, after the Fifth Doctor story, "Planet of Fire" had also used the volcanic landscape as a location for the planet Sarn, and the beaches as a location for the beaches of, well, Lanzarote.

https://www.youtube.com/watch?v=qm8aLCba6jc

Correspondingly, the working title for this story was "Return to Sarn," although this is believed to be more a case of misdirection for nosey parkers, than any serious decision to set the story on the planet. The Eighth Doctor had already been back in "Night of the Doctor" in any case.

The Doctor uses one of his Second incarnation's very favorite instructions: "When I say run, run!"

Clara says the school secretary hates her, going on to explain, "She thinks I gave her a packet of TENA Lady for Secret Santa." British viewers will have known that TENA Lady is an underwear liner for women, designed to help control incontinence of the bladder.

The Doctor says that in the future, Courtney Woods "marries a fellow called Blinovitch," implying that her future husband is the person who outlines the Blinovitch Limitation Effect, as referred to in the Third Doctor adventure "Day of the Daleks" — the Doctor explains why he can't go back into his own past to fix mistakes — and several subsequent Doctor Who scripts. The Blinovitch Limitation Effect could be seen when a time-traveler makes contact with his or her own future self, thereby breaking the First Law of Time, it's also related to the kind of temporal paradox that plays out in both "Father's Day" (rewriting history) and "The Wedding of River Song" (time loops).

The Doctor claims to know that the year is 2049 because of "that prototype version of the Bennett oscillator" he spots nearby. In "The Ark in Space," the Fourth Doctor makes a similar assessment of the temporal location of the spaceship the TARDIS has landed in, saying "Judging by the macro-slave drive and that modified version of the Bennett oscillator, I'd say this was built in the early thirtieth Century."

https://www.youtube.com/watch?v=qtk1BE3toOg

In the same story, the Doctor uses a yo-yo to test the efficiency of the local gravity, which the Twelfth Doctor also does here. That yellow yo-yo appeared often in the Fourth Doctor's era, being the kind of thing he would bring out in a dull moment, or to entertain his companion Leela. It would later turn up in the Twelfth Doctor's pocket, dazzling vikings in "The Girl Who Lived."

https://www.youtube.com/watch?v=pvnKXOGYKM8

Whether by accident or design, it's fitting that this episode was first aired on an anniversary of the launch of Sputnik, the first object launched by mankind to orbit the Earth. It was fired into space by the USSR on October 4, 1957.

Tony Osoba, who plays Duke, is a Doctor Who veteran, having appeared as Lan in the Fourth Doctor story "Destiny of the Daleks" and Kracauer in the Seventh Doctor story "Dragonfire." To British viewers he's best known for appearing as the inmate McLaren in the prison-based BBC comedy Porridge.

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