Susanne Sommers Calf Exerciser is a parody of the Thigh Master brand of exercise equipment used to tighten and tone a person's thighs. This product appeared in the Season Six episode, "Fun with Veal".
After the boys stole or rescued, depending on the point of view, the calves from slaughter at a local farm, they appeared weak. When Butters saw this product advertised on T.V. he foolishly bought it mistaking calves the animal with calves of the human anatomy.