Choked to death by her abusive alcoholic father, Jessica Sanders later manifested as an alter ego of her sist Niki, a single parent with her own alcohol issues. Blessed with superhuman strength, she quickly dominated her weaker-willed sibling and proceeded to fool Niki’s husband and son, while taking on assassination jobs for the mysterious Linderman. Not afraid to manipulate or even kill to get her way, Jessica continues to supercede her sister’s personality throughout the first series.
Although many doppelgängers are impossible to tell apart, you’d have no problem distinguishing between Red Dwarf’s Rimmer and his heroic counterpart, Commander Arnold Judas Rimmer. One’s a snivelling egocentric with a giant H on his forehead, the other’s a modest hero who was kept back a year at school when he was seven years old and likes to use the phrase “Smoke me a kipper, I’ll be back for breakfast!” Ace made his first appearance in Season 4’s ‘Dimension Jump’, but proved so popular that he occasionally appeared in future episodes.