The Ballerina
A good-looking woman walks into a bar wearing a tube top. She sits down at the end of the bar and immediately raises her hand to signal the bartender for a beer. At that moment, everybody notices that she doesn't shave her armpits. When she finishes her drink she raises her arm again to get another one. Again, everybody sees her incredibly hairy armpits. This happens a few times.
Meanwhile, a drunk man on the other side of the bar says to the bartender as he passes him, "Hey! D'you see that ballerina on the other side of the bar?"
The bartender gives him a nod.
"Buy her a drink on me."
The bartender replies, "Sure, but how do you know she's a ballerina?"
"Because," answers the drunken man, "any chick who can lift her leg that high has GOT to be a ballerina."