When she sits around the house, she sits around the house

My all time favorite "yo mama" joke is "Yo mama's so fat she sat on a quarter and a booger popped out of George Washington's nose" although "Yo mama's so fat you have to take 2 trains and a cross-town bus to get on her good side" is also excellent material. More conceptual, that last one, blurring the lines between reality and a figure of speech.

I think i just killed it. Here's a vintage YMJ from the 80's: "Yo mama's so fat that when she puts on BVDs they spell Boulevard."

Yo mama for the new generation