Joe Mama's so fat, when she goes in the elevator, she has to go down.
Elevator
Explanation
Explain Bear
Listen up, dummy! The joke is that Joe Mama is so obese that her weight makes the elevator go down. The funny is that elevators go up and down anyway, but the joke implies her weight is the SOLE reason for it. Get it now? Dumbass!
GG Miller
STOP STEALING MY FUCKING JOKE