The subplot with Stan getting beat up by his sister Shelley came from Parker's real-life experiences getting beat up as a child by his sister, also named Shelley, who is three years his elder. Parker said although his sister would later deny it, she regularly beat him up or locked him out of the house for hours; Parker stated that the scene when Stan says "You're my sister and I love you" in order to try to avoid a beating, but was subsequently beat even harder, was based on an actual experience with his sister. The scene in which Stan asks the giant mutant Stan to attack Shelley is based on Parker's childhood fantasy of having a larger version of himself beat up his sister. The resolution to the subplot, in which Shelley takes the blame for Stan's mistakes, and then beats up Stan when he tries to thank her, was also based on experiences Parker had when his sister would bail him out of trouble.