Fun Riddles

Question: Two men are facing each other alone in a large room. There is a clock on the wall. One man, who thinks of himself as a prophet, says to the other, "In five minutes you'll be stabbed in the back."

The other man is very distraught and stares at the clock. After five minutes he is stabbed in the back.

What happened?

Question: 4 people fall out of a boat and only 3 get their hair wet.

Question: What do these things all have in common: Laughter, living well, and a good offense?

Question: I am a big threat to humanity,
but you wouldn't get rid of me even if you could.

What am I?

Question: In Michigan you cannot take a picture of a man in a green hat.

Why?