So yesterday I was labbing stuff and I found an infinite with Lucas. To do it, you have to jump, footstool, up b, then cancel the up b. Here's a video showing it off. And here's a list of characters it works on:
Mario
Luigi
Wario
Falco
SoPo
Charizard
Jigglypuff
Lucario
Sonic
Roy
Marth
Ness...