Yo mama's so fat, Jenny Craig told her, "sorry, I don't perform miracles!"
Yo mama's so fat, her yearbook picture was a satelite photo.
Yo mama's so old, her breakmilk is now cheezwiz.
Yo mama's so fat, the Sun orbit around her.
Yo mama's so fat, when she became an astronaut scientists declared the discovery of a 10th planet.
Yo mama's so poor, she can't afford to pay attention.
Yo mama's so stupid, she thought a quarterback was a refund.
Yo mama's so stupid, she thought a Colin Powel was a punctuation mark.

Yo mama's so nice, she gave me a dollar when I asked for a quarter... Totally unrelated, but felt I had to say something nice since I've been insulting everyone's mama.