[DS9] Season 2, Episode 23 (Netflix: S2 E23): Crossover
This episode mainly gets a 3 for being fun. They try to recapture the sentiment from the first mirror-universe episode (from TOS, “Mirror, Mirror“), but it’s also a little upsetting learning the results of that episode.
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Read more at Memory Alpha
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Notes:

Mirror-Kira tries really hard to act sexy. I’ve heard that a lot of people were enchanted by this Kira. I think she’s ridiculous

She talks about how Kirk influenced Mirror-Spock to reform humanity…and it led to them being overrun and enslaved by an alliance between Klingons and Cardassians. That’s depressing.

So then Sisko gets them out of there. He says he’ll start fighting back. Is this supposed to give us hope? Because episode in TOS ended in a similar way but it apparently led to the demise of all of humanity
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