3. Career-defining character work
This is one of the rare TOS hours that gives a showcase to almost every major bridge character while still delivering a focused plot. Kirk gets to play diplomat and trickster, improvising his way through a murderous hierarchy and ultimately appealing to Mirror Spock’s logic and integrity. Spock, even with the famous goatee, remains recognizably himself, coolly rational, suspicious of Kirk, yet open to the possibility of a better future, which deepens the Kirk–Spock dynamic across realities.
Uhura, Scotty, and McCoy all get standout beats: Uhura weaponizes her presence and charisma to outmaneuver Sulu on the bridge, Scotty leans into his “miracle worker” reputation as he engineers the transporter fix, and McCoy’s refusal to abandon an injured Mirror Spock reinforces his Hippocratic principles even in enemy territory. That ensemble emphasis gives “Mirror, Mirror” an emotional breadth that many other season 2 episodes lack.