The size of Mom's butt and hips constantly fluctuates between scenes, being largest in the waiting room and smallest in the laboratory.
When Dexter sits on top of Mom's butt, the position of his hands change from in front of his legs, to behind them, then back again between shots.
In "Sister Mom," when Dee Dee (as Mom) sticks her tongue out at Dexter, the color of her pants changes to that of her shirt, then back again as Dexter's name is called.