The planet from this episode and the previous one ("Patterns of Force") look exactly the same from orbit.
In the wide shots of Kirk and Rojan fighting, the faces of the stunt doubles can be seen.
Trivia: There are some nice nods to previous events. Rojan mentions the energy barrier at the edge of the galaxy and Kirk nods that they've encountered it -- as they did in "Where No Man Has Gone Before." Later, Kirk reminds Spock of his use of telepathy to confuse a guard in "A Taste of Armageddon."
Rojan states that they can't send a message to Andromeda because no transmission can penetrate the energy barrier. So why not just go past the barrier and then transmit? But they never do this.
Spock states, once on board the ship, that they cannot destroy the central projector because it is constructed out of material they cannot breach. So why not just use the transporter to beam it out into space? As a matter of fact, why not just transport the whole lot of Kelvans out into oblivion?
In the scene where Spock and Rojan are playing chess and they are talking about Kirk kissing Kelinda, when Spock says "Captain Kirk seems to find her quite attractive", the camera is close up on his face but his lips do not move.
Kirk moves his eyes and Uhura blinks when they're paralyzed, despite the fact that Rojan neutralizes "nerve impulses to the voluntary muscles."
When Scotty gets drunk and tosses an empty bottle away, there's a dubbed-in sound of glass breaking, but when he collapses, the bottle is unbroken at his feet.
The Kelvans neutralize all non-essential personal. This includes everyone except Kirk, Spock, McCoy, and Scotty. Why are Kirk and Spock essential? With Rojan commanding, what is Kirk really supposed to be doing? Also is a science officer really needed now that the ship's mission is no longer to explore. Yet Rojan keeps them around but he doesn't keep around the helmsman or navigator.
Scotty: (kissing his empty bottle of liquor) We did it, you and me. Put him right under the table.
Rojan: We do not colonize. We conquer. We rule. There is no other way for us.
Kirk: Being human does have certain advantages -- being able to appreciate the beauty of a flower, of a woman.
Kirk: (while fighting with Rojan) You thought I was taking your woman away from you. You're jealous! You tried to kill me with your bare hands. Would a Kelvan do that? Would he have to? You're reacting with the emotions of a human. You are a human!
Rojan: No, I cannot be! (shoves Kirk to the door as Spock and McCoy enter and catch him)
Kirk: I'm stimulating him. (McCoy pushes him back into the fight)
Spock: Humans are very peculiar. I often find them unfathomable, but an interesting psychological study.
Rojan: These shells in which we have encased ourselves -- they have such heightened senses. To feel, to hear, to smell. How do humans manage to exist in these fragile cases?
Rojan: At least we'll be away from all this openness. No, this is too strange for us. We are creatures of outer space. Soon, we will be safe in the comforting closeness of walls.
Rojan: Captain, we can control the Federation as easily as we can control you. The fate of the inferior in any galaxy.
Kelinda: This business of love...you have devoted much literature to it. Why do you build such a mystique around a simple biological function?
Kirk: We enjoy it.
Kelinda: The literature?
Kirk: Kelinda, I'm sorry I brought up the whole subject.
Kelinda: Do you really regard this touching of the lips as pleasurable?
Kirk: I did.
Kelinda: Curious. Let me try.
Scotty: I found this on Ganyroom... uh Ganymede.
Tomar: What is it?
Scotty: It's...um, green.
Rojan is played by Warren Stevens, who co-starred as "Doc" in the 1956 movie, Forbidden Planet. Creator Gene Roddenberry has been quoted as saying Star Trek was heavily inspired by that movie, often regarded as the first serious, big budget, high concept science fiction movie.
Desilu No: 5149-50.
References a line from Shakespeare's Romeo and Juliet. Speaking about Romeo, the man she loves but who bears the name of her family's enemy, Juliet says "a rose by any other name would smell as sweet", in other words even he were not called Romeo he would still be the man she loves.