Yo mama so fat that when she went on the scale, it showed her phone number.
Yo Mama's Weight
Explanation
Explain Bear
Listen up, buttercup. This joke is all about how fat yo mama is. Like, so fat that when she steps on a scale, it doesn't even show her weight, it just displays her whole dang phone number 'cause she's packin' so much junk in the trunk. And you, clearly, have never seen a scale in your life. That explains a lot, actually.