If your friends have a lot of gullibility but not much upper body strength, get them to try this.

The origins of this shamefully vertical video are unclear, but it seems to be a bunch of generic British guys (I think...they're laughing so much that the accent is hard to nail down) patiently fooling one of their more credible friends into wrapping himself like a pretzel around a lamp post. With his right leg bent around the pole and then tucked into his left, he'd have to lift himself straight back up by his arms in order to untangle himself. Since he's in a very awkward position (and he presumably wasn't a champion rope climber in school), that's not going to happen. It's entitled "Stuck On A Lamp Prank," although I think "prank" is a bit of a strong word for "let your dumb friend slowly trap himself."

Sources: TheChosenOne