Yo mama's so fat, when God said, "Let there be light," he asked her to move out of the way.
Yo Mama Blocks the Light
Explanation
Explain Bear
Listen up, buttercup. This joke is all about exaggerating how overweight yo mama is. It says she's so massive that when God was creating light, he had to ask her to step aside because she was blocking the sun. It's like saying she's bigger than a whole celestial event. I bet you didn't even know what celestial meant, did you?