Originally posted by
Tiny Turtle:
Fish could start swimming backwards, morph into a different species or whatnot.
Oh cool, an Escher aquarium! I want!
Edit: A cuttlefish is enough material to be the subject of it's own screen saver. You wouldn't just be talking about programing interesting behavior, you'd have to give it some kind of AI, those little guys are smart. I was pretty amazed by how they hunted together when I saw a couple in Belize.