On an overseas flight, a lawyer and an elderly man were in adjoining seats.

The lawyer asked the senior if he’d like to play a little game. The older man was tired, and he told the lawyer he only wanted to sleep.

But the lawyer insisted the game was a lot of fun.

“Here’s how it works,” he said. “I’ll ask you a question. If you can’t come up with the answer, you have to give me a pound. Then it’s your turn to ask me one. But if I can’t answer it, I have to give you £20.”

The senior figured if he just got this over with, maybe he could get some sleep. So he agreed to play.

The first question from the lawyer was “How far apart are the earth and the moon?”

The senior stayed completely silent, reached for a dollar, and gave it to the lawyer. Then he said, “My turn. What walks upstairs backwards and comes downstairs forward?”

The lawyer was stumped. He thought and thought. He tried to remember all the riddles he knew. He searched every corner of his brain.

He even cheated and asked the flight attendants and other passengers.

Finally, he gave up. He woke up the older man and gave him a twenty. The senior stuffed the twenty in his coat and went immediately back to sleep.

The lawyer couldn’t stand it. He woke up the older man and said, “I have to know. What walks upstairs backwards and comes downstairs forward?”

The senior got out his wallet, gave the lawyer a pound, and went back to sleep.