I got the kittens a rechargable ball that rolls around on its own and everyone's very confused by it. They're playing with it, but they're looking at it like it's doing something insane and inexplicable. It was advertised as exercising their predatory instincts, but prey usually runs *away* from the predator, not just in completely random directions, including very fast directly toward the predator. Maybe "play" is a bit of a strong word. They're following it around and occasionally batting it.