See, he's been complaining that he has a "monobrow."
See, Mom said, "I can fix that; just ask me to sometime."
See, he got a sudden urge to fix it himself.
See, he now has two half-eyebrows.
I figure, it's a pretty cheap object lesson. Eyebrows grow back.
"But Mom, can't you fix them somehow?"
"You know, pencil or something?"
"A, I don't own an eyebrow pencil, as I don't play the draw-on-facial-features game. B, even if I did, trust me, it would look FAR worse..."
And maybe the next time he's tempted to jump on an impulse with No Thought Whatsoever (tm) all I'll have to say is "Remember the Eyebrows!" Kinda like the Alamo...