Scotty: What a mess.
Spock: Picturesque descriptions will not mend broken circuits, Mr. Scott.
McCoy: Traces of argon, neon, krypton. All in acceptable quantities. However, I wouldn't recommend this place as a summer resort.
Spock: Thank you for your opinion, it will be duly noted.
Spock: I realize that command does have its fascination, even under circumstances such as these, but I neither enjoy the idea of command nor am I frightened of it. It simply exists, and I will do whatever logically needs to be done.
McCoy: Mr. Spock, life and death are seldom logical.
Spock: But attaining a desired goal always is.
Spock: It is more rational to sacrifice one life than six.
McCoy: I'm not talking about rationality.
Spock: You might be wise to start.
Spock: I'm frequently appalled by the low regard you Earthmen have for life.
McCoy: Respect is a rational process.
Ferris: What do you intend to do?
Kirk: Do? I intend to continue the search, inch by inch, by candlelight, if necessary, until the last possible moment. If you'd keep your nose off my bridge, I'd be thankful.
Spock: Your tone is increasingly hostile.
Boma: My tone isn't the only thing that's hostile, Mr. Spock!
Spock: The logical thing for you to have done was to have left me behind.
McCoy: Mr. Spock, remind me to tell you that I'm sick and tired of your logic.
Spock: That is a most illogical attitude
Yeoman Mears: I don't want to die here!
Spock: Infinitely preferable to the kind of death we would be granted on the planet's surface.
Boma: I admire your ability to make so measured a choice.
McCoy: It may be the last action you'll ever take, Mr. Spock, but it was all human.
Spock: Totally illogical. There was no chance.
McCoy: That's exactly what I mean.
Kirk: Uh, Mr. Spock, there's really something I don't understand about all of this. And maybe you can explain it to me. Logically, of course. When you jettisoned the fuel and ignited it, you knew there was virtually no chance of it being seen, yet you did it anyhow. That would seem to be an act of desperation.
Spock: Quite correct.
Kirk: We all know, and I'm sure the doctor agrees, that desperation is a highly emotional state of mind. How does your well-known logic explain that?
Spock: Quite simply, Captain. I examined the problem from all angles, and it was plainly hopeless. Logic informed me that, under the circumstances, the only possible action would have to be one of desperation. Logical decision, logically arrived at.
Kirk: Aha, ha ha. I see. You mean you reasoned that it was time for an emotional outburst.
Spock: Well, I... wouldn't put it in exactly those terms, Captain, but...
those are essentially the facts.
Kirk: You're not going to admit that for the first time in your life, you committed a purely human, emotional act?
Spock: No, sir.
Kirk: Mr. Spock, you're a stubborn man.
Spock: Yes, sir.
In several scenes the "fake" nature of the rocks is clearly visible. When a spear misses Spock and hits the nearby rock, chips of what are clearly lightweight styroform fly off. When DeForest Kelley pulls the "boulder" off of Leonard Nimoy's leg, his grip visible deforms it.
Shield and spear props were scaled down and given to Buck Maffei to make him look larger, then larger ones were used when the Enterprise crew handled them. In the shot where a shield is dropped on the crew, a scaled down shield is used in the first shot but the larger one in the second, making it appear that the shield has expanded.
Gaetano's sideburns change shape several times from pointed to straight and back again.