A guy walks into a bar with his pet alligator...

...and the bartender says, "Hey! Get that thing outta here!"

The guy says, "Wait, wait, he's totally harmless. I've had this alligator since he was a baby and I've trained him to be completely under my control."

Dubious, the bartender says, "I don't know if I believe you, and I think it will still scare my customers, so please just leave."

"Listen," the man says. "If I can prove it to you and everyone in here that this alligator is completely harmless, will you let me stay and have a drink?"

So the bartender agrees, albeit a bit apprehensively, not sure what the man has in mind. The man then commands the alligator to open its mouth and the beast does. The man then sticks his head inside the alligator's gaping maw, and the crowd gasps, but the alligator doesn't bite down. Finally, the man pounds his fist on the top of the alligator's head three times and still the animal's jaws remain open.

The man removes his head from the alligator's mouth and says, "See, he's completely harmless. In fact, I can do this trick with anyone! Who here wants to give this a try?"

A blonde stands up in the back of the bar and says, "Okay, I'll give it a shot, but please don't hit me on the head that hard."