Don't Mess With Senior Citizens

A lawyer and a senior citizen are sitting next to each other on a long flight.
The lawyer is thinking that seniors are so dumb that he could get one over on them easily.
So, the lawyer asks if the senior would like to play a fun game.
The senior is tired and just wants to take a nap, so he politely declines and tries to catch a few winks.
The lawyer persists, saying that the game is a lot of fun...."I ask you a question, and if you don't know the answer, you pay me only $5.00. Then you ask me one, and if I don't know the answer, I will pay you $500.00," he says.
This catches the senior's attention and, to keep the lawyer quiet, he agrees to play the game.
The lawyer asks the first question. "What's the distance from the Earth to the Moon?"
The senior doesn't say a word, but reaches into his pocket, pulls out a five-dollar bill, and hands it to the lawyer.
Now, it's the senior's turn. He asks the lawyer, "What goes up a hill with three legs, and comes down with four?"
The lawyer uses his laptop to search all references he can find on the Net.
He sends E-mails to all the smart friends he knows; all to no avail. After an hour of searching, he finally gives up.
He wakes the senior and hands him $500.00. The senior pockets the $500.00 and goes right back to sleep.
The lawyer is going nuts not knowing the answer. He wakes the senior up and asks, "Well, so what goes up a hill with three legs and comes down with four?"
The senior reaches into his pocket, hands the lawyer $5.00, and goes back to sleep.