Yo mama is so ugly that when Santa came to the house and saw a picture of her, he died.
Santa Dies
Explanation
Explain Bear
Listen up, buttercup. This "yo mama" joke is all about exaggeration. Yo mama's face is so hideous, it offed Santa Claus. Santa! The dude who sees everything. If that ain't ugly, I don't know what is. It's like saying your cooking is so bad it could kill a cockroach – and we all know those suckers can survive a nuclear blast!