A few minutes later: another PROOOOOOTTTTTT.
We did our usual bedtime ritual and then came another PROOOOOOOTTTTT.
So I said to him, "I'm going to give you a new nickname. You're my BFF. Big Fart Factory."
He replied casually with his usual calmness, "Oh yeah?"
And then a few seconds later I went PROOT. :-D
So he said, "Okay, then you're LFF. Little Fart Factory."
I replied, "Fair enough."