Well, you answered your own question. We grow older and put faces to those headless creatures and realize that...it's just those damn turtles! No, but seriously, the monsters as children are our fears as adults. They're just not monsters anymore. They're, just like everyone is agreeing with, the human race. For instance, being afraid of clowns that are just here to make us laugh grow up to be that boy or girl that jokes on you all the time...just to make people laugh. Think about it.