Wig head (couldn't spell manniquin)....jk
You need a car with a sun roof. You get the wig head and act like it's a real person standing up with their head out of the sun roof. All of a sudden, you slam on the brakes, and the head goes flying. Or, you drive past one of the Jackass gang and they hit the head with a baseball bat or golf club Like Tiger's ex-wife did. Again, the head goes flying, hopefully to scare the shit out of some unsuspecting bystander.
I've been a fan since the show started and got a lot of people to watch it, too, including my grand kids. I know, this won't earn me any brownie points, just sayin'
That's not the wig head above and you can't use it in the prank...it's a crappy pic, anyway.