It's a staple of bad comedy, but I've never actually seen a pair of these things in person. Then I did, at the Dollar Tree and decided to pick it up. It's made of cheaper material and doesn't really make the clacking noise you'd think it would, but for $1 it's a nice little novelty item.
It's a wind up toy, and for some reason it chatters at near hypersonic speed. (hyperbole) But it's more fun than you would think, so a good value.