"Closing Time" is that rare thing — a Cyberman adventure that is sweet and touching, and revolves around the values of family, heart and home. It's also the adventure that introduced the idea of the Doctor being able to translate the words of babies and plays with some of his supposed extra powers, including an imperious shush.

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

(The episode is available on iTunes and Amazon.)

Gareth Roberts worked on a script with the working title "Three Cybermen and a Baby," a spoof of the movie Three Men and a Baby. His other working titles included "Everything Must Go" and "The Last Adventure."

Although it seems crucial to the story now, Daisy Haggard's role as Sophie was reduced because she was appearing in the play Becky Shaw at Almeida Theatre in London during filming for this episode.

Craig and Sophie's child Alfie was played by seven babies in total. The character was originally written as a girl called Grace, later changed to Tess. And the crucial inclusion of the Doctor's dialogue with Alfie/Stormageddon was added at the last minute by Steven Moffat, having come up with it while writing "A Good Man Goes to War." Steven also wrote the final two scenes, to make them work with the overarching story of River Song.

When the Doctor is working in the toy shop, he describes his remote controlled plane as going "up tiddly up" and "down tiddly down." This is a nod towards the lyrics of the song "Those Magnificent Men in their Flying Machines," taken from the movie of the same name:

https://www.youtube.com/watch?v=UPgS26ZhqZs

The choice of names for the fictional department store Sanderson and Grainger isn't entirely clear, but a clue to the latter surname may come from the eternal British comedy series Are You Being Served? The head of the men's department at Grace Brothers was Ernest Grainger, referred to throughout the series as Mr. Grainger.

The Doctor is seen opening and laughing at a children's book called Daisy's Wild Ride, by Bob Graham. This may be because it's a first introduction to science, with experiments for families to try. In the book, Jane sends her pet pig downhill on a cart, which ends messily for all concerned.

During the fight scene with the Cybermat, Matt Smith managed to break the most complicated Cybermat model — the one with the teeth — with a frying pan. It had to be repaired with tape in order to keep shooting.

The Doctor talks about visiting the Alignment of Exidor, the name of which may well be a nod to the '70s sitcom Mork and Mindy. In that show — also the story of aliens living in a domestic human environment — Mork and Mindy have a conspiracy theorist friend called Exidor who believes in aliens.

In the scene where the Doctor has to jump through Craig's french window, there was some trouble getting the scene quite right. First the door frame was too small for Matt Smith's stuntman to jump through safely. Then the rebuilt door was too big to fit shatter glass — the safety glass used in stunts of this nature, so the production team had to use safety glass (which breaks into chunks) and a small explosive to blow the glass at the right time.

Lynda Barron's involvement, playing the Doctor's friend Val, marks a crossing point between two traditions in the revived Doctor Who series, the bringing in of iconic comic actors, and the bringing in of actors who appeared in the classic series. Lynda would be best known to British viewers for her role as nurse Gladys Emmanuel in the TV comedy Open All Hours (also the title of this episode's Doctor Who Confidential), but she appeared twice in classic Who. Her voice appears in the First Doctor cowboy epic "The Gunfighters," singing "Ballad of the Last Chance Saloon," and she played Wrack in the Fifth Doctor adventure "Enlightenment."

NEXT: 10 Things You May Not Know About ‘The Wedding of River Song’

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