Robert Underdunk Terwilliger Jr., PhD, better known as Sideshow Bob, is a recurring character 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 arch-enemies.

Allen Kelsey Grammer is an American actor. He gained fame for his role as psychiatrist Dr. Frasier Crane on the NBC sitcom Cheers (1984–1993) and its spin-off Frasier. At more than 20 years on-air, this is one of the longest-running roles played by a single live-action actor in television history. He has received numerous accolades including a total of six Emmy Awards, three Golden Globe Awards, a Screen Actors Guild Award and a Tony Award.