Jokes that are commonly used to dis
both the victim of the joke and his/her momma such as Yo Momma's so fat, stupid, ugly, poor...and so on.
If watching your friends make them up isn't enough, there is a show on MTV called "Yo Yomma" where the best jokes win.
Here are examples of some classic yo momma jokes.
Yo Momma's so fat she saw a bus go bye and shouted, "stop that twinkie!"
Yo Momma's so stupid she got hit by a parked car.
Yo Momma's so poor that when her ciggarette went out she said, "Where did the heat go?"
Yo Momma's so fat she farted in the Gulf of Mexico and caused Hurricane Katrina.