The Fourth Dimension
David Troughton is the son of Second Doctor, Patrick Troughton. He's not directly related to new series director Alice Troughton, though! After Georgia Moffett, he's the second progeny of a past Doctor actor to appear in Series Four. David previously appeared in three Doctor Who stories: 1967's The Enemy of the World (uncredited), 1969's The War Games and 1972's The Curse of Peladon.
'Molto Bene' is Italian for 'Very Good'. We first heard the Doctor say it in 2007's The Family of Blood.
Third Time Lucky
Lesley Sharp has starred in two previous Russell T Davies productions - Bob and Rose and The Second Coming. The latter also starred Ninth Doctor Christopher Eccleston.
This episode was originally intended to be episode 8, before Steven Moffat's two-parter, but was pushed back to episode 10. The name of the shuttle bus, Crusader 50, was a reference to it originally being in the 50th episode of the new series to be screened.
Room Of Doom
The majority of the episode is set in just one room. This is similar to several other claustrophobic thrillers, such as Hitchcock's' Rope and more recently, Flightplan.
Colin Morgan, who plays Jethro, previously appeared with Catherine Tate in her 2007 Christmas special. He has also recently been cast in the title role of the upcoming BBC production, Merlin.
There's No Place Like Home
Midnight is one of very few stories not to feature the TARDIS (except in the title sequence). The last time this happened was in 1975's Genesis of the Daleks.
Uniquely for Doctor Who, we don't get to see even a glimpse of the Doctor's adversary, nor find out its name.
Holidays From Hell
Things went horribly wrong the last time the Doctor went on a holiday and encountered passengers on a 'space bus', too - see 1987's Delta and the Bannermen.
The music video that is screened in the Crusader 50 is the track 'Do it, do it again', by Raffaella Carra.
Compiled with the help of Peter Ware.