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"Star Trek: Voyager" (1995) More at IMDbPro »

Yes, and it's all about the ranks of certain characters. From the beginning Tuvok was apparently meant to be a Lieutenant, but in the pilot episode "Caretaker" was given the rank pips of Lieutenant Commander - two silver, one black. This was allegedly a wardrobe error. Cashiered former Starfleet officer Tom Paris was given the rank of full Lieutenant (two silver pips) and Maquis crewmember B'Elanna Torres was given the rank of Lieutenant Junior Grade - one black strip, one silver on her rank pin. She was seemingly promoted to Lieutenant Full Grade at the end of the following episode, "Parallax", when she is made Chief Engineer (two silver strips on her rank pin). However, during the 12th episode of the first season, "Cathexis", the mistake with Tuvok's rank was spotted and corrected. At the same time it was also evidently decided to "demote" Paris and Torres, both to Lieutenant Junior Grade. This was probably done to maintain a reasonable chain of command, and possibly because it was felt they should not hold the same rank as one of Captain Janeway's trusted and most senior officers. As a result there are several continuity errors as Tuvok and Paris' ranks change back and forth due to the shooting schedule; they retain their original ranks for the sequences set on the bridge, but the revised ones are shown in all other scenes. Torres' rank pin is revised in all her scenes, again a result of the shooting schedule.

From a story point of view, it has been inferred that Tuvok and Torres are both demoted as a result of their actions in the previous episode, "Prime Factors", where they undermine Captain Janeway's authority and are summarily disciplined, though any demotions are never seen or referred to onscreen. While plausible, this theory does not account for the continuity errors in the following episode or the change in Paris' rank, though. In the fourth season episode "Revulsion", Tuvok receives an on-screen promotion to Lieutenant Commander, with no reference to any demotion.