Rich Man, Poor Man (1976)

S14E6 Peter's Sister

Karen, Peter's sister, shows up for Thanksgiving and starts picking on him just like Meg does. Initially, Meg finds it funny, but her sympathy kicks in, and she chooses to assist Peter in preparing for a wrestling showdown against their sister. Meanwhile, Stewie and Brian want to steer clear of binge eating during the holiday, so they embark on a cleanse, but Stewie takes it to an extreme level.