The creature creator is really ridiculous -it's simple and quite intuitive, you start out with a torso and add limbs, eyes, mouths, ears, appendages, weapons, and a scad of crazy details in whatever number and configuration you want. You name your critter, and you set 'em loose. In the creator, you can make the critters, then interact with them a little (make them do various silly things, take pictures, etc.) When the full game comes out, you can load your favorite critter into the game, and you can share the creatures with other users. Other user's creatures will also inhabit your world, and be in competition with your own.
So here is my creation, the Nurpletail. Here he is playing with three baby nurpletails, teaching them to dance. It's kind of absurdly adorable, isn't it?