We hope we don't spoil too much when we say that Sam Rockwell plays multiple roles in this week's indie sci-fi drama Moon (the trailer already gave that away). And the insanely hard-working Rockwell, who has quietly become one of our generation's finest actors, knocks it out of the park. After watching him, we were inspired to survey the other great actors throughout cinema history who had to portray multiple roles in a movie. Some had to star opposite themselves; some had to portray different characters in different sections of a given film. We decided to exclude cameos (sorry, Ben Stiller in The Cable Guy!). And there are several we couldn't make room for (feel free to leave angry comments about Meg Ryan in Joe Versus the Volcano and Michael J. Fox in the Back to the Future sequels). Nevertheless, here's our list of the Ten Greatest Multiple-Role Performances in Movie History.