The Mirror Universe is the setting of several narratives in the Star Trek science fiction franchise, a parallel universe existing alongside, but separate from, the fictional universe that is the main setting of Star Trek. It resembles the main Star Trek universe, but is populated by more violent and opportunistic doubles of its people.[1][2] The Mirror Universe has been visited in one episode of Star Trek: The Original Series,[3] five episodes of Star Trek: Deep Space Nine,[1][4] a two-part episode of Star Trek: Enterprise,[5] a storyline woven through the first season of Star Trek: Discovery (continuing with a Mirror Universe character in the main cast of seasons 2 and 3),[6] and several non-canon Star Trek tie-in works. It is named after "Mirror, Mirror", the Original Series episode in which it first appeared.[7]