Here's some:
-Yo mama's teeth so bad, it looks like her tounge was in jail.
-Yo mama is so stupid she sold her car for gas money.
-Yo mama so stupid she thought the movie "dumb and dumber" were about her parents.
-Yo mama's so ugly, she went to a strip club, and they paid her to keep her clothes on!

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Arguing on the internet is a lot like being in the special olimpics: win or lose, at the end of the day, you're still retarded.