This episode features four firsts regarding Vulcans: it is the first episode to feature the planet Vulcan, the first in which Vulcans other than Spock are seen, the first to feature the Vulcan salute and the first in which the phrase "Live long and prosper" is heard.
This episode marks the first appearance of Walter Koenig (Ensign Pavel Chekov) on the series. However, the first episode which Koenig filmed was "Catspaw
This is Leonard Nimoy's favorite episode of the series.
T'Pau (Celia Lovsky) would later be seen as a young woman in the Star Trek: Enterprise
" and "Kir'Shara
", in which she was played by Kara Zediker
. According to dialogue in those episodes, she was born in 2122 and was therefore 145 years old at the time of this episode.
McCoy: Jim, when I suggested to Spock that it was time for his check-up, your logical, unemotional first officer turned to me and said, "You will cease to pry into my personal matters, Doctor, or I shall certainly break your neck."
Kirk: Sailor's luck, Mr. Spock. Or as one of Finagle's Laws puts it: "Any home port the ship makes it'll be somebody else's, not mine!"
Sulu: How do you figure it, Chekov? First we're going to Vulcan, then we're going to Altair, then we're headed to Vulcan again. Now we're headed back to Altair.
Chekov: I think I'm going to get spacesick.
Spock: It has to do with...biology.
Kirk: What kind of biology?
Spock: Vulcan biology.
Kirk: You mean the biology of Vulcans?
Spock: Biology as in... reproduction?
Kirk: Well, uh...there's no need to be embarrassed about it, Mr. Spock. It happens to the birds and the bees.
Spock: The birds and the bees are not Vulcans, Captain. If they were... if any creature as proudly logical as us...were to have their logic ripped from them...as this time does to us... How do Vulcans choose their mates? Haven't you wondered?
Kirk: I guess the rest of us assume that it's done... quite logically.
Spock: Captain, there is a thing that happens to Vulcans at this time. Almost an insanity, which you would no doubt find distasteful.
Kirk: Will I? You've been most patient with my kinds of madness.
T'Pau: Spock, are our ceremonies for outworlders too?
Spock: They are not outworlders. They are my friends.
T'Pau: Art thee Vulcan, or art thee human?
T'Pau: Combat commences with the lirpa. If both survive the lirpa, combat continues with the ahn-woon.
McCoy: What do you mean, 'if both survive?'
T'Pau: This combat is to the death.
Spock: After a time, you may find that 'having' is not so pleasing a thing, after all, as "wanting." It is not logical, but it is often true.
T'Pau: Live long and prosper, Spock.
Spock: I shall do neither. I have killed my captain...and my friend.
McCoy: You can't tell me that when you first saw Jim alive, that you weren't on the verge of giving us an emotional scene that would have brought the house down!
Spock: Merely my quite logical relief that Starfleet had not lost a highly proficient captain.
Kirk: Yes, Mr. Spock, I understand.
Spock: Thank you, Captain.
McCoy: Of course, Mr. Spock, your reaction was quite logical.
Spock: Thank you, Doctor.
McCoy: In a pig's eye!