This woman is sitting in a bar, wearing some sort of tube top. She has never shaved her armpits in her entire life, so as a result, she has a thick black bush under each arm. Every 20 minutes, she raises her arm up and flags the bartender for another drink.
This goes on all night. The other people in the bar see her hairy pits every time she raises her arm. Near the end of the night, this drunk at the end of the bar says to the bartender, "Hey, I'd like to buy the ballerina a drink".
The bartender replies, "She's not a ballerina. What makes you think she's a ballerina?"
The drunk says, "Any girl that can lift her LEG that high has to be a ballerina!"