Season 3: Episode 31: Mr. Griffin Goes to Washington
Peter's toy company gets bought by a large cigarette company, and the toys are then used to market cigarettes to children. When Peter, on Lois's advice, confronts his new bosses about their evil use of toys, they promote Peter to president to shut him up. Lois, pleased with all the perks that come with Peter's new position, keeps her mouth shut too, while Brian quits smoking in protest. Peter's bosses send him to Washington to lobby against a bill that would put them out of business, because they figure politicians will be able to relate to a big dumb fat guy. When Lois finds Stewie smoking a cigarette, she goes down to Washington to stop what Peter's doing, and Peter ends up getting his tobacco company fined $100,000,000.