Here's a few:
Your teeth are so yellow, I can't believe it's not butter!
Your mama's so stupid, she stole a free sample.
Your mama's so stupid she walked into a school bus and said,"Where's the cream filling?"
Your mama's so fat, the last time she saw "90210" it was on a scale!
You're so stupid you stuck a battery up your butt and said, "I GOT THE POWER!!!"
You're so poor, I went to your house for dinner and there were 3 beans on a plate. I took 1 and your mom said, "Don't be greedy!"
You're so poor that when I went to your house and stepped on a cigar, your mom said, "Who turned off the heater?"
You're so poor when I went to your house, your mom said, "Get into the car," and everybody sat down on a skateboard.
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Funny, eh?