The genius says to the idiot, "If I ask you a question and you don't know the answer, you have to give me $5, but if you ask me a question and I don't know the answer, I have to give you $1,000.

The idiot agrees.

The genius asks the idiot, "What is H2O?"

The idiot thinks for a minute and then hands the genius $5.

The idiot says, "Ok, my turn. What walks on 2 legs but sleeps on 3 legs?"

The genius thinks and thinks, but he cannot come up with an answer so he hands the idiot $1,000. The genius, curious as to what the answer is, asks the idiot, "So what is the answer?"

The idiot hands the genius $5.