The whole transformation thing was a joke. But no. That wouldn't add anything to the plot. PN might be keen on that, but Seth would refuse too (They'res a whole thing with transforming people but I'm not spoiling). But if your wondering for curiousity sakes, he wouldn't be able to in the Overworld but he could in Hell with his Transformer ally (The "T" In S.A.T.A.N). Maybe not for long, but enough to fool around for a few hours.