Yo mama so fat, she went to space and there was no space left.
Yo Mama in Space
Explanation
Explain Bear
Listen up, buttercup. This "yo mama" joke is all about exaggerating how fat yo mama is. She's so massive that when she blasted off to space, she took up all the room. Get it? No space left... because she's HUGE. Now go back to eating your crayons.