An oldie, but seems appropriate given one of the threads this past week:
A guy walks into a bar and pulls a tiny grand piano out of his pocket. Then, he pulls out a little guy who sits down and begins to play. "Where'd ya get that?" the bartender asks. "I have a magic bottle; you rub it and get a wish," the customer replies. The customer agrees to let the bartender try it, and pulls a grungy old whiskey bottle from his pocket. The bartender rubs it, and the room fills up with ducks, flying and pooping everywhere. "I didn't wish for a million ducks", says the bartender. "So, did you think I wished for a ten inch pianist?" responds the customer.