The Hitchhiker's Guide to the Galaxy (2005)

Visible crew/equipment: When Ford runs past the caravan to chase the Vogons with a towel, you can see the cameraman, and about 4 other crew members reflecting in the caravan's surface.

Slartibartfast: You must come with me, quickly or, or you'll be late!
Arthur: Late for what?
Slartibartfast: What? Oh, no...What is your name, earthman?
Arthur: Dent. Arthur Dent.
Slartibartfast: Late, as in the late Dentarthurdent. It's a kind of threat, you see.

Trivia: The Magrathean answerphone message is played by Simon Jones, who plays Arthur in both the TV series and the radio series.

Question: What was the purpose of Arthur borrowing Marvin's arm?