My favorite piece of character development in TOS is Spock finally learning to get out of the way of oncoming vehicles.

I finished The Art Nouveau styled set :>
Title: it ends or it doesn't
Fandom: Star Trek: The Original Series
Ship: McCoy/Spock/Kirk
Rating: T / no major warnings
Word Count: 28k (lmao)
Written for @mcspirkevents' mcspirkbingo (my bingo card is here)
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McCoy dies, and Kirk breaks his hand on a wall. Kirk dies to save McCoy, and McCoy breaks his hand on Spock's face for not stopping him. Spock dies, and he doesn't have to see what happens next, because the day resets. The day keeps resetting. McCoy keeps dying.
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“Spock, get him out of here, will you?” McCoy says, turning that crooked half-smile on Spock, and Spock focuses on his next inhalation, his next exhalation.
“Open the door, Dr. McCoy,” he says.
McCoy rolls his eyes, but Spock's far more focused on the faint trembling in McCoy's hand. “C'mon,” McCoy says, “this is the logical solution, Spock. Someone has to stay. I'm already here. You two can move faster than I can, anyway. Get him back to the ship.”
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(all my fic is still ao3-locked (sorry) but if you need an invite lmk)
i'm 10 minutes into watching star trek ii: the wrath of khan
& bones got kirk some reading glasses for his birthday kirk is like 50 years old or whatever & i was like "that's kind of a boring gift"
but spock gave kirk a real paper book so i was just realizing spock probably told bones he's getting kirk a book, bones realized kirk's goddamn midlife crisis won't allow him to buy himself a pair of reading glasses already at the age of like 50, so he gave him glasses just so he could actually enjoy the gift spock got for him
spock, mr logical emotionless vulcan, got kirk a really sweet sentimental gift but one that he'd probably just leave on a shelf if bones hadn't gotten the boring practical gift cuz it's a SET. THEY COMPLETE EACH OTHER.
ot3..........