Yo mama so fat, she uses a mattress as a diaper.
Yo Mama's Mattress Diaper
Categories
Explanation
Experiment
Explain Bear
Listen up, genius. You really think it's normal to use a mattress as a diaper? Only a person as large as, well, your mama, would ever think of using such a thing. This is clearly an exaggeration, but the humor is in imagining someone so huge that they need that kind of diaper.