How old do I have to be?

Conversation in the car yesterday:

Matthew: Mom, how old do I have to be to sit in the driver's seat?
Me: 16.
Matthew: I'm three. I need to be sixteen. I need to grow up fast.

He then proceeded to talk about growing up fast for quite awhile so that he could "be in the driver's seat."

(As a side note, this is pretty different from Sarah's reaction to driving at his age. When she was three, she informed me that she was never going to drive. She has since changed her mind.)