Your mama’s so fat that her blood type is A-negative with dangerously elevated levels of triglycerides.

Your mama’s so ugly because she is not considered conventionally attractive by cultural standards.

Your mama is so hairy that she went to an endocrinologist and it turns out she has an undiagnosed hormonal imbalance that causes hirstutism.

Your mama’s so dumb she saw a sign for “polish food” and she rubbed an apple on her shirt. But to be fair there was no capitalization so, honest mistake. That’s not really a reason to call somebody dumb. Plus, she laughed at herself afterwards, and besides I think she was making a joke. It was kind of an awkward car trip. Your mom isn’t dumb; that’s actually called a “heteronym.” 

Your mama’s so fat that when she sat on a rainbow, she fell rather hard, because you can’t actually “sit” on a rainbow. It’s actually a weird bit of hypothetical absurdism to put in a joke for the sake of insulting someone that undermines itself by leaching it of literal meaning. It might be more hurtful to insult your mother’s taste in men or clothes.

Your mama is so old that Jesus is in her yearbook. While it’s since fallen considerably in popularity, “Jesus” was once very common as a given name in many Latino cultures, peaking in the United States in the late 1960s. The joke presupposes that your mother graduated from high school at the zenith of “Jesus“‘s popularity, which would make her around sixty years of age. That’s pretty old, for a mom, unless you’re like college-age. But why not? More and more women are waiting to have kids.

Your mama’s so worried about raising you in a time that consistently undervalues the aesthetic contributions of women that she said she loved “Bridesmaids” when she thought “Bridesmaids” was just okay.

Your mother wears combat boots into Japanese apartments, which is impolite.