McCoy: The word (desert) conjures up pictures of dunes, oases, mirages. Sunlight, palm trees.
Spock: We're 900 light-years from that kind of desert. The precise meaning of the word 'desert' is a waterless, barren wasteland. I fail to understand your romantic nostalgia for such a place.
McCoy: It doesn't surprise me, Mr. Spock. I can't imagine a mirage ever disturbing those mathematically perfect brain waves of yours.
Spock: Thank you, Dr. McCoy.
Trelane: Oh, how absolutely typical of your species! You don't understand something so you become fearful.
Trelane: Dear Captain, so many questions. Make the most of an uncertain future. Enjoy yourself today. Tomorrow...(ominously) may never come at all.
McCoy: Does your logic find this fascinating, Mr. Spock?
Spock: No. "Fascinating" is a word I use for the unexpected. In this case, I should think "interesting" would suffice.
Trelane: Do you know that you're one of the few predator species that preys even on itself?
Trelane: Don't fret, Captain. I'm only a bit upset with you, but this Mr. Spock you mentioned, the one responsible for that unseemly, impudent act of taking you from me, which is he?
Spock: I'm Spock.
Trelane: Oh, surely not an officer. Isn't quite human, is he?
Trelane: Well, I don't know if I like your tone. It's most challenging. That's what you're doing, challenging me?
Spock: I object to you. I object to intellect without discipline. I object to power without constructive purpose.
Trelane: Oh, Mr. Spock, you do have one saving grace after all - you're ill mannered. The human half of you, no doubt.
Trelane: She has the same melting eyes as the Queen of Shiba and the same coloring.
(After Kirk has destroyed his power source)
Trelane: Oh, the remarkable treachery of the species!
Kirk: Go on, Trelane! Look at it! It's over. Your power is blanked out, you're finished!
Trelane: You've earned my wrath! Go back. Go back to your ship! All of you! And prepare: you're all dead men! You, especially, Captain!
Trelane: How do you plead?
Kirk: I haven't come to plead in your court, Trelane.
Trelane: Anything you might say has already been taken down in evidence against you.
Trelane's Father: Stop that nonsense at once! Or you'll not be permitted to make any more planets!!
Kirk: He was probably doing things comparable to the mischievous pranks you played when you were a boy.
Spock: "Mischievous pranks," Captain?
Kirk: Yes--dipping little girls' curls in inkwells, stealing apples from the neighbors' trees, tying cans on -- forgive me... Mr. Spock. I should have known better.
Spock: I shall be delighted, Captain.
William Campbell's muttonchops are very obviously fake.
DeForest Kelley mispronounces "Jaegar" several times.
Supposedly the distance between Gothos and Earth is 900 light years, as stated several times. However, this wouldn't work since it would put the "present" in the 27th or 28th century, and the series is set in the 23rd century.