i'm a big fan of animations that play with the art form. Duck Amuck, of course, was of the most famous examples, along with the Fleischer's Out of the Inkwell series. here's a 1991 Oscar-winning short by Daniel Greaves that plays like a lost Don Hertzfeldt film (I can imagine that Don was at least a little inspired by it while thinking up "Genre"). this really must've taken quite a long time -- the moves are so well choreographed and timed together. enjoy:
here's a later CG short by Richard Jack and Daniel Greaves about the secret life of billiards balls from 2001 called Rockin' & Rollin'