A man walks into a bar, doesn't have any money. He goes over to the bartender and says,
"So, bartender, I don't have any money, can I get a drink?"
"Hell no."
"Alright, how about a bet then? Ten dollars says I can bite my eye."
The bartender thinks, "No way someone could do that", so he agrees. "Sure."
The man takes out his glass eye and bites down on it.
The bartender, being a good sport and loving a good trick, says okay and gives the man ten dollars. The man goes, spends it all on drinks, and comes back again.
"I bet you twenty dollars I can bite my ear."
The bartender is a little weary, but he thinks about it, and says, "No way you can do that! You're on!"
The man takes out his false teeth and bites clamps them on his ear. The man laughs, and gives the guy his twenty dollars. Once again the man goes, spends it all, and returns to the bartender.
"Fifty bucks says I can stand on the bar and pee into a shot glass, and not spill a drop."
The bartender says to himself, "There's no way someone could do this", so he agrees.
The man gets up on the bar, aims, completely misses. Piss is everywhere - the bar, the stools, and even on the bartender. Not a drop in the shot glass. The bartender starts laughing, and so does the man. This confuses the bartender.
"Why are you laughing? You just lost fifty dollars!"
"True," the man replies, "but I bet that guy over there a hundred I could piss all over the bartender and he'd laugh."