Dave and I joke that Ben is like a little wind-up toy because of the way he crawls around the house, his butt wiggling rapidly from side to side.
Actually, Ben is better than any toy his big brother and sister have ever had. They crack up at his babbling ("DIGGA DIGGA DIGGA DIGGA!"); giggle when he stabs a finger into the air as he shows off his newfound pointing abilities; and laugh uproariously when he splashes in the bathtub.
Yesterday, they discovered that if you put batteries in him, his feet will go and go. OK, actually, he doesn't require any batteries.