Be careful what you ask for

Driving along a country road, a man saw an old lady, obviously in distress, at the side of the road. "Are you ill?" he asked her. She looked up "You'll have to speak up" she croaked "I'm a bit deaf". "Are you OK?" he shouted. "I'm tired and I need a drink" she said. The man got a bottle of water out of his car and gave it to the old hag. "Thanks, dearie" she said "Now I'll do something for you. I'll grant you one wish - anything you want". The man thought for a moment, then shouted his wish into her ear. "Take this stone", she said, "And when I'm out of sight, rub it and your wish will come true". "Thanks very much" said the man, and drove off. When she was out of sight, he stopped his car,and gave the stone a rub. At first, he thought nothing had happened, but then he could hear the faint sound of a piano. There on the back seat was a little man in black tails playing a small grand piano. "What on earth!" shouted the motorist. "I'm what you wished for" said the little man, "A twelve-inch pianist".