If you pay close attention to the model in Rayman 2, you'd notice that the inside of his ascot there is a curious blue circle, and on the bottom of his neck, there's a similar orange circle. Some would say that this is because the shading back then wasn't so great, but the truth is obvious.

Portals.

Obviously, every organ he needs to survive are in his head, and the other parts are just there to allow him to move.