Episode Behind the Scenes


Barbara Luna, who plays Marlena, would later play Veronica in "In Harm's Way", an episode of the fan-made series "Star Trek: New Voyages".
When Kirk and the evil Spock fight, Kirk swings his elbow at Spock's jaw and you can clearly see he misses...but Spock reacts anyway.
On the Enterprise bridge, Chekov is wearing a gold sash on his waist and a dagger on his right hip. He leaves the bridge and goes into the elevator. A moment later Kirk joins him but Chekov's gold sash and dagger are now missing. Instead, he has the agonizer device on his waist. When the elevator doors open, his gold sash and dagger reappear.
In the overhead shots, the stunt men playing McCoy and Scotty in the sickbay fight don't look much like Kelley and Doohan either.
When Kirk and company beam onboard the I.S.S. Enterprise, the ship is orbiting in a clockwise direction in the savage universe, contrary to the U.S.S. Enterprise, which was orbiting the Halkan homeworld in a counterclockwise direction in their universe. Yet, throughout the rest of the episode, the I.S.S. ship is orbiting the Halkan homeworld counterclockwise. (This is corrected in the remastered edition.)
At the beginning Kirk calls for beam-up and drops his arm. But when he beams up and appears on "his" Enterprise before switching, his arm is still upraised with the communicator in it.
Kirk punches the Imperial crewman that helps him in the face, but when the guy falls on the ground he's holding his side.
When the evil Kirk yells at Spock from the edge of the brig doorway, you can see his chest extend outside the light beams that show where the force field is.