Yo' mama

Any insult that fits the following pattern:

Yo momma is so [derogator attribute], she ....

For instance:

• Yo momma is so poor she can't afford to pay attention.
• Yo momma is so nasty she made Right Guard turn left.
• Yo momma is so ugly, when she goes into a bank they turn the security cameras off.
• Yo momma is so dumb it takes her 2 hours to watch 60 Minutes.

The genre is so big that Google even has a single page dedicated to sites with Yo Momma jokes (Recreation > Humor > Jokes > Yo Momma Jokes).

Yo' mama so fat, she went to the movies and sat next to everyone.
Yo' mama so old, she still owe Jesus a quarter.
Yo' mama so nasty, I had phone sex with her and she gave me an ear infection.
Yo' mama so fat, she jumped up in the air and got stuck.

Yo mama like community college - everybody be gettin in.
No wait, yo mama more like a shotgun: two cocks, she blows.
Yo mama so big she on both sides of the family.
She go to the movies and sit down next to everybody.
Yo mama so stupid, she entered the pepsi challenge and chose Jif.
Yo mama so fat you can't see her legs, it just looks like she glidin across the floor.
Yo mama so fat she irons her jeans in the driveway.
The bitch has to put on lipstick with a paint roller to save time.
Yo mama teeth are so damn buck, I used her to rake my yard.
Yo mama so poor, the elevator at the Welfare office is her 'mobile home'.
She so poor, the welfare checks got her picture on em.
And food stamps got your daddy's picture on em.
Yo mama house so small, the welcome mat just says, 'well?'
Yo mama tripped and when she fell she created that Grand Canyon you been hearing so much about.
Then the bitch was like, 'whats the number for 911!?'