Is that an expression?

"Mommy is that an expression?"
This is what we hear from Ethan quite often.
You know those phrases that you really don't mean but you say anyway?

"I'm so tired I could sleep for a week!"
or "It's so cold, my hands are going to freeze off!"

It all started when one day I was rushing into the house and I said, "If I don't get to the bathroom, I am going to die!" and I may have even said I would wet my pants too but the "I'm going to die" part really bothered him. I know I should have been thinking about what I was saying in front of my 4 year old but I just wasn't. So, I had to explain that sometimes we say things that are just "expressions." Hence, the "is that an expression" question we get from him all the time.

So here is the latest "expression" story:
Ethan and Steve were at the Post Office last week and Steve was mailing something for one of his bands. The postal worker noticed "Blair Artist Management" as the return address and asked Steve what kind of artists he managed. So Steve told him he worked with Christian artists. He replied that he was a "an old Christian music dinosaur." At that point Ethan started pulling on Steve's shirt telling him to pick him up. Finally Steve picks him up and he is looking the man up and down and all around. They finish up and then walk to the car and Ethan says, "Daddy, you know why I asked you to pick me up? That man said something about a dinosaur and I wanted to see if he had dinosaur skin." And yet again Steve had to tell him it was "only an expression."