Gamespy Story.

Now, suddenly, his creature could walk. And he did so -- he walked right out of the sea and onto the land. This incredible moment in the history of evolution was made even more remarkable by the technology behind it: the game had figured out, procedurally, how a creature would walk if it had three legs (it was a kind of lopsided gait, if you're curious, with three steps: left, right, then middle.) No 3D modeler created the creature, and no 3D animator was required to make it move around -- it was all created out of a gamer's whim and a computer program smart enough to make it work.
IGN Story.

This is literally amazing. Talk about thinking outside the box, Will Wright got tired of dealing with gigantic teams of animators, coders, etc and just made the actual program smarter. It knows how things will evolve, walk, act, build, and basically live, yet still gives you plenty to do. Sounds like a game to definetly keep your eye on.