Yo momma's so old her hobby is evolving.
She's so stupid the last time she heard "pi r squared" was when she used the wrong baking tray.
She's also so stupid that when she worked at an M&M's factory, she alphabetised them and threw away all the Ws.
She's so fat the last time she stood on the weight scales it said her phone number and told her to move her vehicle.
EDIT: Yo mamma's so stupid she can create you and it's still an improvement on the last generation
...Sorry, I couldn't choose.