While the bar tender is busy cleaning glasses, a snail crawls onto the bar. "Gimme a beer," it says to the bar tender. 
The bar tender looks around, no-one is waiting so he carries on.
"Hey you," says the snail "I said gimme a beer".
Eventually, the bar tender's eyes fall in disbelief on the snail.
"Are you gonna serve me, or what?"
So the bar tender picks up the snail between his thumb and forefinger, and flicks him out of the door. 
Next New Year's Eve, the same bar tender is serving in the same bar. The same snail crawls onto the bar and asks "What did you do that for?"