Another result of a lunch discussion with Lewis. In Super Mario Galaxy 2, the lumas (the star creatures) have a little planet that functions as a space ship and Mario uses it to travel across the galaxy. For some reason, when he first gets control of it, it takes the shape of his head. I can't remember if it's a magical planet that automatically does that, if the lumas made it so of their own free will, or if Mario whipped them into submission and forced them to re-build it for him. I'm assuming it's the last.