Sweet cheeks.

Tristan: Mom, I really need new underwear.

Me: Why?

Tristan: Mine don't fit anymore.

Me: Is the elastic too tight, how do you know?

Tristan: Because...my cheeks hang out. (In a whisper) You know my butt cheeks."

I thought I was gonna die laughing. So now he has big boy boxers. No cheek problems. And all is well with the world.