Sideshow Bob
After receiving numerous death threats in the mail—most of which are written in blood—Bart becomes paranoid. He soon learns the culprit is his arch-enemy, Sideshow Bob, who is incarcerated in Springfield State Prison, sent the notes, wanting revenge on Bart for imprisoning him twice ("Krusty Gets Busted" and "Black Widower"). The next day, Sideshow Bob is paroled because the parole board no longer considers him a threat to society. When the Simpsons visit a cinema to see "Ernest Goes Somewhere Cheap", Sideshow Bob sits in front of them, smoking and laughing obnoxiously. The Simpsons realize that "he" sent the letters and threatened to kill Bart. Homer and Marge angrily tell him to stay away from their son.