Do the characters show some sort of tornado effect when changing into those robotic monsters? The description sounds extremely familiar.. I'm pretty sure I've got a "Oh no more games!" CD laying around somewhere with a demo of that game. Have to search for it though,

(edit: it's probably number 7 or 9 or something from the "Ohh no more games!" CDs , I think the one with the One must fall demo on it)

Cheers