Yo mama!

[deValdr]

Yo mama so fat, I tried to drive around her, but I went out of gas.

[PK8]

Your mum is so fat, she fell in love and broke it.

[Ace]

Your mum is so fat, when she wears a yellow shirt and jumps from a skyscraper, everyone thinks the sun has set (don't know if it's grammatical right, just translated it xD)

[PK8]

Your mum's so stupid, she stayed in the grocery store for a day staring at a gallon of orange juice just because it said "concentrate".

[deValdr]

Lols XD
This is old, but classic:
Yo mama so fat she wore a yellow raincoat and people yelled "Taxi!"

[Ace]

xD
Your mum is so fat, she has to zoom out in google earth an make a screenshot for a passport photo.

[Captain Wow]

Your mom is so stupid she sits on the TV and watches the couch

[Ace]

Your mum is so fat, 3 other mums are circling in her orbit.

[No ID]

Yo mama so black, that I tired to giver a ride home last night and the cops pulled me over for tinted windows.

[Wyatt]

Yo mamas so old aristotle wrote the very first yo mama joke... about yo mama.