A man walks up to the bartender and says, "Y'see that cup over there? I'll bet $100 that I can piss in it from here!" The bartender readily agrees, because the shot glass is way over on the other side of the bar. So the man unzips and whips it out, then pisses in a million different directions, coming nowhere even close to the shot glass. Meanwhile the bartender's laughing so hard he can barely breathe.
"Pay up," gasps the bartender, so the man walks over and grabs $400 from a third guy playing pool. The bartender asks, "Why did that guy give you the money?"
And the first guy says, "'Cause I bet him $400 I could piss all over your bar and you'd just laugh about it!"