 Wallace Wolodarsky had seen the 1991 version of Cape Fear and pitched the idea of spoofing the film . Jon Vitti was then assigned to write a parody of the original Cape Fear film from 1962 as well as the remake ( both films are based on the 1957 novel by John D. MacDonald , entitled The Executioners ) . Instead of using the spoof as only a part of the episode , which could have contained a B @-@ story , the entire episode was devoted to this parody . Sideshow Bob was cast as the villain and Bart became the main victim . The episode followed the same basic plot outline as the films and used elements from the original film 's score by Bernard Herrmann ( which was also used in the 1991 version ) , which , after this episode , became Sideshow Bob 's theme . This episode marked the first time a Sideshow Bob episode was not a mystery . 
