Nitpick: It has been established in many other episodes of the Star Trek universe (including Deep Space Nine) that the transporter technology has numerous built in safeguards against weapons and/or uninvited guests. None of which were triggered when Mirror Bareil beamed onto the station's Central Operations transporter during a time of war. Even if the automatic systems were somehow disabled, there was enough time to set up a force field to contain the subject until an identification could be made.
Nitpick: Sisko has security clear a path to Landing Pad A to allow Mirror Bareil and Kira to depart. The landing pads are in a bay above the habitat ring, as shown in "Emissary". However, the outside shot shows the runabout docked at a pylon.
Nitpick: Given the history of other Mirror Universe inhabitants coming through the main transporter pad in ops, without a ship present, it doesn't make sense why, after detecting Antos coming aboard, to have met him without an armed guard.
Goof: Kira calls Bareil's Bajoran phaser a disruptor two times.
(after Dax tries to fix her up with one of men she used to date)
Kira: Sometimes your taste in men frightens me.
Jadzia: I'll make sure to tell Worf you said so!
Worf: Tell me what?
Jadzia: Don't be so nosey!
Indendant: I'd be very disappointed if you didn't find the major... intoxicating. After all, she is me... Or the next best thing to me.
(talking about Bareil)
Kira: He used to say: 'When you overindulge the body...'
Mirror Bareil: '...you starve the soul.'
Kira: You're not going to kill anyone. Not with that disruptor. The power cell's cracked.
Bareil: How long have you known?
Kira: Since we left ops.
Bareil: Then why'd you come with me?
Kira: I needed the exercise.
Jadzia: What about Doctor Trag'tok? He's intelligent, a good physique, and he has a very opaque cranium.
Kira: True, but his eye bothers me.
Jadzia: Which one?
Kira: The middle one.
Scott Strozier (Security Guard) was also in Star Trek: First Contact.
During the scene in Worf and Dax's quarters, in the background, on a shelf you can see a trophy. That is the trophy that Worf received when he won "Champion Standing" at the Bat'leth tournament on Forcas Three in The Next Generation episode "Parallels". Of course, in some of the realities to which Worf shifts, he only wins 9th place, and in some, he doesn't even compete. However, in 'our' reality he wins the tournament and is awarded this trophy.
This episode re-uses footage from "Empok Nor", when Mirror Bareil goes to the docked runabout.
Cirroc Lofton (Jake Sisko) does not appear in this episode.
This episode marks the last appearance of Philip Anglim on the series.
This episode reveals Bareil's given name to be Antos.