Sideshow Bob, whose full name is Robert Underdunk "Bob" Terwilliger Jr., is a recurring antagonist in the animated television series The Simpsons. He is a self-proclaimed genius and a former sidekick on Krusty the Clown's show who turned criminal mastermind after being mistreated. He is notorious for his elaborate revenge plans against Bart Simpson, whom he sees as his archenemy. Voiced by Kelsey Grammer, Bob is characterized by his sophisticated, cultured personality and distinctive transatlantic accent. His storylines often involve him being released from prison to carry out vengeance, usually thwarted by Bart and Lisa Simpson. Bob has become one of the show's iconic villains, appearing in many episodes, comics, video games, and even the Simpsons Ride at Universal Studios. The character was first introduced in the episode "The Telltale Head" and had his first major storyline in "Krusty Gets Busted," where he framed Krusty the Clown for armed robbery. Subsequent episodes explore his continued plots against Bart and the Simpson family, often marked by dark humor and cultural references. Sideshow Bob is also known for his love of high culture, musical talents particularly in Gilbert and Sullivan operettas, and his evolution from a non-speaking sidekick who communicated with a whistle into a fully voiced villain with complex schemes and personal vendettas. Additionally, a notable episode titled "Sideshow Bob Roberts" features him rigging a mayoral election in Springfield to gain political power, showcasing the character's versatility in the series as both a criminal mastermind and a comedic villain.