What goes up a mountain with three legs and comes down with four legs?

A lawyer and a Chinese sit side by side on a long flight. The lawyer thinks that all Chinese are so stupid that he could easily outsmart them. So, the lawyer asks the Chinese man if he'd like to play a fun game. The Chinese guy is tired and just wants to take a nap, so he politely declines and tries to catch a few winks. The lawyer persists and says the game is a lot of fun. I'll ask you a question, and if you don't know the answer, you only pay me $5; ask me once, and if I don't know the answer, I'll pay you $500, he says. This gets the Chinese man's attention, and to shut the lawyer up, he agrees to play the game. The lawyer asks the first question.

The Chinese doesn't say a word, reaches into his pocket, pulls out a five-dollar bill and hands it to the lawyer. Now it's the Chinese man's turn. He asks the lawyer, "What goes up a mountain with three legs and comes down with four?" The lawyer takes his laptop and searches the internet for all the references he can find. He emails all the smart friends he knows, but all to no avail. After an hour of searching, he finally gives up. He wakes up the Chinese man and gives him $500. The Chinese guy pockets the $500 and goes right back to sleep. The lawyer goes insane because he doesn't know the answer. He wakes the Chinese man up and asks, "What goes up a mountain with three legs and comes down with four legs?

The Chinese man reaches into his pocket, gives the lawyer $5, and goes back to sleep......