5. BEING JOHN MALKOVICH
Charlie Sheen enjoys a brief but pivotal cameo as, well, himself in Spike Jonze's surreal comedy. John Malkovich (also as himself, obviously) discovers that he is losing control of his body and possibly his mind, and consults his best friend Sheen who, in the scene embedded below, attempts to discern if Malkovich is actually on drugs, while playing with a Rubik’s cube. The part was originally meant for Kevin Bacon.
No-one said this was a straightforward movie.