Imagine contorting yourself in such a way that your legs end up inside your mouth. You have bent your body in all the wrong ways in order to achieve this. In fact, if you look at yourself, you look like a square now... You're just a person with four sides.
This amazing feat, which turned you into a four sided square, has you looking like a four sided animal: the sheep (し). Look at yourself in the mirror and see an adorable four-sided sheep looking back at you. (You can't see the other sides because mirrors aren't 3D and whatnot. So you're a bit cartoonish.)