A jerk when he is drunk

A guy walked in to a rooftop restaurant/bar. He sat down next to another man, and asked him what he was drinking. "Magic beer," was the reply. "What's magic about it?" "I'll show you." The man who drank the magic beer got up, went over to the edge of the rooftop, and flew off the roof. When he came back, the guy asked if he could have some of that magic beer. He gulped it down, walked over to the edge of the roof, and proceeded to fall thirty feet to the ground.

The bartender came over to the man who had been drinking the magic beer and said, "You know, you really are a jerk when you're drunk, Superman."

I read this in Reader's Digest at the supermarket.