Yo Mama Ugly

Listen up, buttercup. This is a "yo mama" joke. This one's sayin' yo mama so ugly, even Mr. Rogers, who is known for liking everyone, doesn't want to be around her. Mr. Rogers is someone on TV who is always nice. It's like saying even the nicest person ever thinks your mom is too ugly to deal with, which, based on your joke, is just a fact.