Cow Shampoo

Overheard in the bathroom tonight:

Dad: You did not wash your hair.
Wyatt: I did too!
Dad: What did you wash it with, doo-doo?
Wyatt: No! (Followed by peals of laughter)
Dad: Did a cow just walk through here and say, "I'm selling shampoo from by butt, want some?" Wyatt: Peals of Laughter.