A guy's sitting at a bar, drinking a beer and minding his own business, when the guy sitting next to him nudges him.
"Hey?"
"Huh?"
"Hey, guess what? Up on the roof here, there's this spot where the wind from the alley is just right, that if you jump off, the draft will blow you back up to the roof!"
The guy rolls his eyes. "You've had a few too many," he says, and turns back to his beer.
"No, no, I'm serious! It's totally real! I'll show you! Go outside and watch as I jump!"
The guy looks a bit weirded out, but he goes outside and looks up, and the other guy climbs up onto the roof, takes a running start, and leaps off. Sure enough, he falls a few feet, then suddenly reverses direction and floats back up to land atop the roof again.
"See? Wanna see it again? Watch!" The man takes a running start, leaps... and floats up to the roof. "It works every time!"
So the first guy, seeing it actually demonstrated in front of his eyes, decides he's gotta try it for himself. He goes back in, makes his way to the roof access, and climbs up to find the other guy waiting for him. He shows him exactly where the point to jump from is, so he steps back, takes a few deep breaths, runs towards the edge, leaps...
...and plummets to the concrete below, breaking every bone in his body.
The second guy goes back down, sits at the bar again, and orders another beer. The bartender looks at him and shakes his head slowly, sighing at him. "You sure are a jerk when you're drunk, Superman."