DiSser X posts 2 bands on the same movie soundtrack. DiSser Y replies with the movie.

X: David Bowie and David Sylvian
Y: Merry Christmas Mr Lawrence

Ah, shit. That's not a good example. Bowie acted in that movie. Erm, whatever.... 2 bands/musicians involved in some movie in any which way possible and then name the movie, that's the game.