Joe mama so fat, she could not walk the stairs of heaven.
Credits: to my friend.
Joe Mama's Heavenly Ascent
Explanation
Explain Bear
Listen here, you big dummy. "Yo mama" jokes are usually all about making fun of someone's mom. In this case, they are saying that Joe mama is so fat that she can't climb the stairs to heaven, so it is implying that she is very large. You probably can't even lift a small rock.