Ya that show is messed up
What I don't get is how they can risk something like that, what if the (pranked) victim actually fought back and hurt one of the actors? I'm not saying for sure (though I hope I would) I would have run in and attacked the knife wielding guy unarmed, but I've seen a couple episodes and I know I would fight back in some of those situations.
Unless of course the entire thing is fake.