So there are a bunch of Internet pranks where you trick people into sitting in front of a computer to play a game—one that usually requires intense concentration on the screen. At some point, Linda Blair's demonically possessed face from The Exorcist (or some similar frightening face) pops up and screams, and it usually scares the living shit out of people—sometimes sending them flying out of chairs, sometimes making them piss their pants.
In this example of proud parenting, a dad sets up his unsuspecting son. The kid is so young, this is F-ed up beyond belief, but, man, is it funny (Child Protective Services, where are you?!):
These other clips are also hilarious—the last of which shows how a guy is so scared he pisses himself. Enjoy these, cruel world: