Whether due to alternate universes or weird transporter malfunctions, several Star Trek characters have met their doubles. Doppelganger storylines have been a trope of Star Trek since one of the earliest episodes of Star Trek: The Original Series season 1, episode 5, “The Enemy Within.” Almost every Star Trek series since has featured at least one story where a character encounters an alternate version of themselves. This trope is not unique to Star Trek, of course, as many science fiction and fantasy stories have found creative ways to incorporate multiple versions of the same character.