Humor is subjective, so whether "Yo' momma" jokes qualify as funny will depend on individual preferences. Potentially funny examples include: “Yo' momma so dumb, she thought 'Wu Tang' was an African orange drink” and “Yo' momma so fat, when she turns around, people give her a welcome back party!”
There are many varieties of Yo' Momma jokes that range from making fun of a mother's appearance to making fun of her intellectual level. The first part of the joke sets the stage for the second part. For example, a “Yo' momma so fat” joke ends making fun of a mother's weight, while a “Yo' momma so old” joke makes fun of her age.