A married couple takes their son to the circus. After a while the father gets up to get some popcorn. While he is away the little boy notices something hanging down between the elephants legs.

"Mommy, what is that hanging down on the elephant?" he asks.

The embarrassed mother says "Oh, that's nothing honey," and is relieved when the father returns with the popcorn.

Not satisfied with the mother's answer the little boy waits until his mother leaves to use the bathroom and asks his father, "Dad, what is that hanging down between the elephant's legs?"

Dad answers, "That's the elephant's penis." 

The little boy says, "Well how come when I asked mom she said that it was nothing?"

Dad leans back and says "Son, I've spoiled that woman..."