You don't have to brush all of your teeth...just the ones you want to keep...

Mom: Brady come brush your teeth before school.

Brady: Okay.

* Brady comes into bathroom & begins brushing his teeth; a minute passes. *

Mom: Are you still brushing your teeth?

Brady: Yes.

Mom: Are you getting all of the teeth in the back too?

Brady: I thought I only had to brush the ones I wanted to keep?

Mom: Brady, that's a joke.  You need to brush all of your teeth, not just the front ones.

Brady: Fine.  I'm brushing them all.

Mom: Do I need to come check them?

Brady: No Mom, I reached all the way back to my lungs!

Mom: Good job buddy!