This guy and this girl are rampantly having sex. During a lull in the passion, the guy asks the girl to turn over.
"Why?" asks the girl.
"Because I want to try something different," says the guy.
"That's perverted!" says the girl.
"What did you say?" asks the guy.
"I said that's perverted."
"I'm sorry, I'm not quite sure I heard properly - what did you say?"
"I said that's perverted."
"Shit," says the guy, "that's a big word for a five year-old."