2.31. A train pulls into a station, but none of the
waiting passengers move. (MN)

2.31 answer: It’s a model train set.

2.31a. Variant: The Orient Express is derailed and a kitten plays
nearby.

2.31a answer: The Orient Express is a model train which has been left
running unattended. The kitten has playfully derailed it. (from Bernd
Wechner)