"Yo Mama so fat that she inspired Mulg The Ancient to go on a diet!"
"Yo Mama so fat that a bloat thrall got one look at her and said 'Damn! What did they fill her up with!?"
"Yo Mama so ugly that Absylonia gave her a brown paper bag and said, "here - you need this more than I do!"
"Yo Mama so old that she used to babysit Zevanna Agha!"
What do you got?