Movies where someone is thrown into a situation far different from what they're used to. Usually comedies, but not necessarily.

Some that come quickly to mind are Encino Man (caveman in modern LA), Crocodile Dundee (alligator hunter in NY and later in LA), Kate and Leopold (1876 Duke in modern NY), My Blue Heaven (mob goodfella in suburban middle America), etc.

What are your favorite fish-out-of-water movies?

Star Trek 4....yeah, Star Trek is a bit corny, but who could not keep from laughing at Spock cursing at the guy on the bus or Scotty trying to talk into the mouse! :D

That's the best one with the TOS crew. Save the whales! :)