He sits on a magic green floating ball, obviously.
This is it. The game's graphics just didn't do the best job of making it clear, so it looks like his body just tapers off to a stump.
Ah. He's actually sitting on that thing? I previously assumed he'd either lost his legs, or that they were inside the... object. Do you have any of his concept art? It'd be neat to see how he was originally envisaged.