Some one make sonic work on Jigglypuff, Im not entirely sure how this works.
;o
I tried putting Lucario over Jigglypuff and after seconds after his entry animation begun, the game froze.
I don't know if it will be the same for putting Sonic over Jigglypuff though, but I wouldn't get my hopes up.
Looking at it, replacing Luigi with Sonic is for now the stablest switch.