How small can a movie be? If you take time out of the mix and go for actual size, that would be atoms, which is exactly where IBM went. Engineers at Big Blue went down to the atomic scale and produced a stop motion animation called "A Boy and His Atom" comprised solely of atoms. The painstaking process resulted in a minute and a half long movie, and while it won't win an academy award, it's still amazingly cool. IBM also put together a 5 minute behind the scenes video showing how "A Boy and His Atom" was made that's worth watching, too.
Check It Out: The Smallest Movie Ever: Made with Atoms