The Protostar crew finally reaches Voyager, but not in the correct timeline.
Tropes:
- Beard of Evil: Mirror Chakotay sports the mandatory goatee. Main Chakotay uses some grease when he tries passing himself for him.
- Bizarro Universe: What little we see of the universe where Rok-Tahk, Zero and Maj'El are stranded for most of the episode seems outlandish enough. The Voyager is apparently crewed with the aliens from "All the World's a stage" and commanded by Captain Tuvix, and the worst trial they meet there is bearing with his vulcano-talaxian cooking.
- Canon Discontinuity: The Terran Empire seems to be still quite active, and more in line with how it appeared in the original TOS episode, while Star Trek: Deep Space Nine established it had long fallen.
- Contrived Coincidence: As in every Trek episode involving the mirror universe, it happens that Mirror Voyager is commanded by Mirror Janeway and Mirror Chakotay, and their cetacean ops is crewed with the evil counterpart of the friendly whale from their universe.
- Good Scars, Evil Scars: The whale in Mirror cetacean ops sports a scar over her eye, which her good counterpart lacks.
- Mirror Universe: After visiting two alternate universes, part of the crew arrives in the Trope Namer, where they are greeted by an evil Chakotay and Janeway.Jankom: Even the whale is evil here!
- Mythology Gag: Mirror Janeway sports an eye implant quite similar to Seven of Nine's.
- Oh, Crap!: Chakotay instantly identifies the mirror universe, and is not happy about it.
- Point of Divergence: The first two universes the crew visit correspond to a single change in history: one where Admiral Janeway died onboard the Infinity, and the other where the crew failed to disable the Living Construct. The "Captain Tuvix universe" point of divergence occurs at least as far back as "Tuvix" (assuming it corresponds to a single divergence from the main universe).
- Rule of Three: Chakotay, Dal, Jankom Pug and Murf travel to three different universes before returning to the main one: first, a timeline where Janeway died onboard the Infinity, then one where the Federation fell to the Living Construct, and finally the Mirror Universe. Maj'El's third hop sends her to Captain Tuvix universe instead (where Zero and Rok-Tahk end up in on their second hop), where she stays until they all return home.
- Ship Tease: Admiral Chakotay and Janeway's reunion seems much more than two friends reuniting. There is also a conspicuous shot of Dal and Gwyn smiling at one another while they hug.
- Spoiler Title: The crew begins hopping between alternate timelines in an episode named after the most famous alternate universe in Trek. Wonder where they will eventually end up.
- Underestimating Badassery: Mirror Chakotay decides to begin torturing the crew starting with "the small cute one", Murph. The rest of the crew plays into it by begging him to leave "the small cute one" alone. Then Murph shows why he's the crew's security officer...
