Robert Underdunk "Bob" Terwilliger Jr., PhD, better known as Sideshow Bob, is a recurring character and the secondary antagonist in the animated television series The Simpsons. He is voiced by Kelsey Grammer and first appeared in the episode "The Telltale Head". Bob is a self-proclaimed genius who is a graduate of Yale University and a champion of high culture, including the adoption of a transatlantic accent, similar to that of Grammer's portrayal of Dr. Frasier Crane from the sitcoms Cheers and Frasier. He began his career as a sidekick on Krusty the Clown's television show, but after enduring constant abuse, Bob framed his employer for armed robbery in "Krusty Gets Busted", only to be foiled by Bart Simpson, and sent to prison. Bob started seeking revenge against Bart while in prison, and the two became feuding archenemies.
Bob made his second major appearance in season three's "Black Widower"; the writers echoed the premise of Wile E. Coyote chasing the Road Runner by having Bob unexpectedly insert himself into Bart's life, threatening to disrupt and end it through murder. Starting with that appearance and thereafter, Bob has assumed the role on The Simpsons of an evil genius. Episodes in which he is a central character typically involve Sideshow Bob being released from prison and executing an elaborate revenge plan, usually foiled by Bart and Lisa. His plans often involve death and destruction, usually targeted at Bart or, less often, Krusty, though he starts targeting the entire Simpson family in season 17. In season 27, however, during the first segment of "Treehouse of Horror XXVI", entitled "Wanted: Dead, Then Alive", Bob finally gets his wish of killing Bart, commenting that he spent 24 years trying to kill a ten-year-old child; however, he becomes bored with Bart dead, so he brings him back to life so that he can repeatedly kill Bart over and over again.