A stranger sat next to Little Johnny on a plane. He turned to the boy and said, "Let's talk. I've heard flights go quicker if you strike up a conversation with your fellow passenger."
Little Johnny, who had just opened his book, closed it slowly. "What would you like to discuss?" he asked.
"Oh, I don't know," replied the stranger. "How about nuclear power?"
"OK," said Little Johnny. "That could be interesting. But first, let me ask you a question. A horse, a cow, and a deer all eat grass—the same stuff. Yet a deer excretes little pellets, a cow produces a flat patty, and a horse passes clumps of dried grass. Why do you suppose that is?"
"Jeez," said the stranger. "I have no idea."
"Well, then," said Little Johnny, "how is it that you feel qualified to discuss nuclear power when you don't know shit?"