Yo mama so ugly when she looked in the mirror, her reflection threw up and ran away.
Yo Mama's Ugly Reflection
Explanation
Explain Bear
Alright, listen up, you simpleton! This joke is all about how ugly yo mama is. Like, so ugly that even her own reflection couldn't stand to look at her and puked then bolted. It's an insult, see? Now go back to playing with your blocks.
ButterCup
Yo mama so ugly that she’s the reason Caillou doesn’t have hair.