likely story

me: "What's that on your shirt, babe?" as the elder lad boards the Honeywagon after school.
him: "I think it's mud."

me: "that's a strange place for mud -- it's just a little bit and right at your collar."
him: no comment.

me: "I ask because I want to know how to treat the stain."
him: "It's chocolate milk.  I got it because it's Thursday -- almost Friday."
*As in, bring on the weekend!  Chocolate milk all around!
 
I've used this logic myself, but the shirt still hasn't come clean...