A stranger sat next to Little Johnny on a plane. The stranger turned to him 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 and replied, "What would you like to discuss?"
"Oh, I don't know," said the stranger. "How about nuclear power?"
"OK," said Little Johnny. "That could be an interesting topic. But let me ask you a question first. 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 leaves 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?"