A stranger is seated next to Little Johnny on a plane when the stranger turns to Little Johnny and says, "Let's talk. I've heard that flights go quicker if you strike up a conversation with your fellow passengers."

Little Johnny, who had just opened his book, closes it slowly, and says to the stranger, "What would you like to discuss?"

"Oh, I don't know," says the stranger. "How about nuclear power?"

"OK," says 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, while a cow turns out a flat patty, and a horse produces clumps of dried grass. Why do you suppose that is?"

"Jeez," says the stranger. "I have no idea."

"Well, then," says Little Johnny, "how is it that you feel qualified to discuss nuclear power when you don't know shit?"