Plot (Spoiler)

Peter becomes so convinced that he is a genius that Brian challenges him to prove it. Peter takes the MacArthur Fellows Program, which reveals that Peter is mentally retarded. While Peter is initially depressed, he observes that people more easily forgive his actions when he states he is retarded, meaning he can get away with a lot of things. While exploiting the perks that come with his handicap he accidentally throws boiling oil on Lois. While she is recovering, Child Protection Services takes away Peter’s custody of Meg, Chris, and Stewie, due to their contention that Peter is mentally unfit to look after them. However, when he is unable to regain custody of his kids and accepts that his family may never reunite, Lois, who fully recovered, enters the house and explains she regained custody of the kids.