Red Dwarf: Season 7, Episode 3

7 - 3: Ouroboros

When two realities converge, the Dwarfers undergo their most terrifying ordeal yet - they bump into a real, live, human woman who's attractive and nice. It's Lister's ex-girlfriend Kristine Kochanski. Kryten immediately goes into jealousy overload mode, convinced she'll steal Lister away from him, and starts plotting her immediate return to her own dimension.