Although he will deny it to his dying breath, he considers Spock his best friend too, different from but equal to his friendship with Jim.
Breathing is underrated as a cure for many of the ailments from which his Captain suffers, especially if Bones disappears from Jim's "radar" for longer than three hours.
Captains are generally older than Jim for a good reason, Bones decides when his friend's youth makes him once again believe he is invincible.
Denying he cares for Spock is one of his great pleasures but Spock knows the truth although he'll never admit it either.
Everyone knows Bones will stop at nothing to take care of all those aboard the Enterprise, unless Jim or Spock also need his attention, in which case everyone else must wait, and they are okay with that.
For too a long time after his divorce from that she-devil, Bones didn't feel worthy of being anyone's friend, until a certain Cadet changed his opinion of himself.
Gravity is Bones' friend, something he wishes there was more of on the Enterprise, especially whenever there is a glitch in the controls which then causes him to have vertigo, again.
Hellfire is nothing compared to an angry Dr. McCoy, a lesson Jim has failed repeatedly to learn.
Ignoring Dr. McCoy's advice is allowed once and only once.
Jambalaya is a dish he cannot stand – he's from Georgia, not Louisiana, he has to explain more than once.
Kindness is fine but he knows a kick in the ass is sometimes a lot more useful.
Leonard McCoy is nobody's fool but he can be persuaded to turn a blind eye for the right reasons.
Medical school could have never prepared him for some of the injuries he encounters while serving on the Enterprise and thinks if he survives to retire, he'll put those lessons to good use for the next generation of Starfleet doctors.
New crewmembers avoid Dr. McCoy because of what they've heard until they have no choice but to visit and find he doesn't really have horns or use a pitchfork as a diagnostic tool.
Office hours are strictly limited – generally limited to 24 hours a day, 7 days a week – making Bones request, again, that Starfleet assign them a third doctor.
Pillows kept disappearing from his Medical Bay, a mystery that was solved when he discovered the pillow fort that "someone" had built in Spock's mostly deserted quarters.
Quit complaining – the words Jim swears he'll see engraved on Bones' tombstone.
Regardless of what the medical texts might say, sometimes a good brandy can cure what ails you.
Southerners are just different, Jim often tells him, to which Bones responds with a polite nod and smile.
Talkin' when he's tired out makes him sound even more Southern, 'specially when he includes some of his grandma's favorite sayins in his ramblin', may she rest in peace.
Underneath his gruff exterior beats a heart that loves passionately and cares beyond measure.
Virginity is meant to be lost, he finally tells a pretty little yeoman who comes to him in tears because she thinks her mama's going to kill her when she finds out.
Watermelon on a hot day – nothin' better.
Xenobiology is not a mystery to him but he's happy to leave the toughest cases to Dr. M'Benga.
Yams – candied, pie, casserole, plain with cinnamon butter – all delights the crew share because of Dr. McCoy's love of them.
Zero population growth on a starship is fine in theory but McCoy knows that unattached crewmembers are going to do what humans have done since time began and sometimes a baby is going to result from it.