Blake knows the words "shart" and "going commando."
You're welcome, world. I won't let him say "fart" because it sounds awful out of the mouth of a four-year-old, we don't let him watch SpongeBob SquarePants because it's so crude, and he knows to excuse himself if he burps or toots.
He does, however, correctly identify the occasional smear in his britches that often (when in public because I don't carry back-up) precipitates him going sans britches under his shorts. Why do things that don't sound funny out of my mouth crack me up to no end when he says them?