“Every moment is a test”: Through the Looking Glass (DS9) vs. The Wolf Inside (DSC)

Sisko and Burnham impersonate their Mirror Universe selves, which leads Burnham to question her faith in herself and in humanity … and leads Sisko to look cool dual-wielding phasers.

“What are you, that you could do this?”: The Enterprise Incident (TOS) vs. Face of the Enemy (TNG)

Troi and Kirk try on Romulan faces, and oppression and espionage test what Troi and Spock are capable of.

“You’re too late, we’re everywhere”: The Adversary (DS9) vs. State of Flux (VOY)

Suspicion and paranoia abound on the Defiant and the Voyager, as shape-shifting impostors and surgically altered spies force Sisko and Chakotay to question how much they can trust those under their command.