A Mug Of Beer

There's a man in the back of the bar playing pool with three other guys. After the game the man walks up to the bar and orders a beer. The bartender pores the beer into a mug and puts it on the bar. The man drinks the beer and sets it back on bar. He calls the bartender over and tells him. I bet you 100 dollars that not only can I piss in that mug on the bar I won't even splash any on the bar. The bartender say ok buddy your on. The man stands up and pulls his junk out and starts pissing. He pissis on the bar stool, pissis all over the bar ,and he even pissis on the bartender. The bartender starts laughing real loud and say ok pay up . The man has a grin from ear to ear when he says a bets a bets mister here's you 100 dollars. As the bartender grabs his money he asks the man why are you so happy you just lost 100 dollars? The man looks at the bartender straight in the face and says I'm so happy because I bet those guys in the back room 500 dollars that not only would you let me piss all over your bar you would let me piss on you and you would be happy about it.