I wish my cat had figured this out. It would save on my litter costs. And at 25 pounds, Buster uses a LOT of litter. Apparently the cat in this video uploaded by miimura on April 28, 2007 learned how to do this on her own--no training.
I love the "oh, this is so boring" expression as the cat looks around the room. And the attempt to flush is interesting, though I think maybe she's doing the same thing that any cat would do in a litter box: trying to bury her urine in the litter.
Do you have a pet that potty trained itself? If so, let us know!