So, I'm sure I'm not the only person who's noticed McCoy's astounding ability to always have whatever drug anybody needs at a moment's notice even though half the time he doesn't even seem to be carrying around a hypospray, let alone every medication ever.
How is that possible?
Well, it really isn't, but let's go with this explanation.
Leonard McCoy and the Magic Hypospray
Dr. Leonard McCoy sighed as he sprawled down on the bed in his quarters after his first shift on the Enterprise. He still wasn't entirely sure how he had managed to find himself in Starfleet, but somehow he was now a doctor on the Federation flagship.
It was going to be a long five years.
Suddenly, McCoy got the peculiar feeling that he was not alone. He sat up quickly and immediately found that the feeling was right.
A man whom he had never seen before was in his room, leaning nonchalantly against the wall near his door, and watching him.
"Who the hell are you?" McCoy growled.
"It doesn't matter," the man told him, "I'm here representing Star Trek."
"You know what, that doesn't really matter either."
"…Okay…" McCoy said nervously, sliding subtly over to the silent alert that would bring security officers to his room.
"Don't bother," the stranger told him, "no one's getting in or out of this room until we're done."
The doctor was beginning to feel very nervous. "What do you want?" he demanded.
"Only to talk," the other man said pleasantly. "CMO is a big job, and I want to make sure you're prepared."
"What the hell are you talking about?" McCoy asked. "I'm not CMO, Piper is." (1)
"Oh, don't worry about it. He'll be gone soon. Gary Mitchell, too. You and Spock are going to be Kirk's friends, confidants, ect. Actually, Kirk and Spock are going to be more than just friends, at least they will be if we can slip it past the censors." (2)
McCoy blinked several times and shook his head. "I'm dreaming," he decided. "I must be dreaming. What did I eat last night?"
The other man chuckled. "Oh, trust me," he said, "this is far from the strangest thing you're going to experience, at least assuming our writers don't fail utterly. But I don't think they will. We've gathered a good team."
McCoy blinked again. "Oh," he said. "Alright, let's assume for a moment that I do believe you. You still haven't explained what you're doing in my quarters."
"As I said, CMO is a big job. It's up to you to keep Kirk, Spock, Scotty, Uhura, Sulu, and Rand alive until the end of the mission. And yourself, of course." (3)
"And the rest of the crew," McCoy pointed out.
The man shrugged. "No," he said, "Not really. They're expendable, especially the red-shirts. Try to take care of them, certainly, but it's okay if some of them die; if a lot of them die, even. It raises tension, and it gives us some great opportunities for angst. But the recurring characters can't die, and you'll probably have to save a lot of random diplomats and such as well.
"Now, given some of the wacky situations we're going to throw at you, you'd need to carry around every drug known to man and then some in order to be truly prepared, and that just isn't practical. So I brought you a present." He gestured to the desk, where McCoy saw a very familiar object.
"It's an ordinary hypospray," he noted.
The man chuckled. "Hypospray, yes. Ordinary, no. You see, this hypospray is powered by the magic of technobabble and the imagination. I know, I know," he added at McCoy's incredulous expression, "but it works. All you have to do is think of a chemical or combination of chemicals, and it will automatically appear in the hypospray. You can carry every drug known to man in a single convineint sample.
"Well, I really must be going. Good luck!" And suddenly, he was gone.
McCoy stared at the space where the strange man had been, and then at the hypospray sitting innocently on his desk, and groaned.
It was going to be a very long five years.
1) Mark Piper, the CMO before McCoy, existed for exactly one episode before disappearing completely. It's unclear why he left, other than the fact that Karl Urban was younger and hotter.
2) Yes, McCoy is observant, and he does know both Kirk and Spock very well. But he also had inside information.
3) This is pre-season 1, so Chekov and Chapel don't exist yet.
This actually still doesn't explain things like the scene in The Apple where Spock gets shot at by poison flowers and, without knowing anything about the poison, McCoy gives him the antidote, but I guess the best explanation for that sort of thing would have to be suspension of disbelief: Sometimes you have to sacrifice a little making sense for your happy ending.