Episode Behind the Scenes


Although the director asked for dark lighting on the bridge of the Defiant to not only create an uncertain atmosphere about the ship, but also to better distinguish it from the Enterprise bridge, the producers for "Star Trek: Enterprise" apparently believed that the dark lighting scheme was normal for that ship and kept the lighting low while filming "In a Mirror, Darkly, Part II".
Ronald D. Moore originally wanted to name the ship on "Star Trek: Deep Space Nine" Valiant, after the ship from "Where No Man Has Gone Before", but later settled on Defiant after the ship in this episode.
When Spock grabs Chekov and says his name the first time, the camera cuts to Chekov and the sound of his scream is on the soundtrack, but his mouth does not move.
Although the guy beaming Kirk in at the end is a lieutenant, the close-up shot is the standard shot of Scotty's hands with the lt. commander braid.
When the Tholians attack and McCoy and Chapel throw themselves around to simulate the impact, the bottles in the background stay perfectly still.
When the orderly attacks McCoy he throws him across the sickbay bed but in the next close-up shot McCoy is stretched out length-wise on the bed.
You can see the stars through the back end of the Tholian ship after the Enterprise hits it with phasers.
  One of the more incredible moments of "state the blatantly obvious" occurs when Sulu uncertainly says to Scotty "I think the Defiant is drifting away from us" only to cut to a shot of the viewscreen to see the Defiant obviously moving away from the Enterprise. To make matters worse, Scotty replies uncertainly with "I think you're right."