McCoy may have learned to be unequivocally half-patient and fully straightforward when it comes to Jim Kirk and the doing of Things That Technology Has Spoiled People For, but he draws the line at hygiene. Showering with sonics may shave grimy skin cells off and be an excellent temporary solution in exam season, but there's a reason soap and water have been the best weapons of choice against bacterial contamination for centuries. Prevention, after all, is the best kind of medicine.
"You are a crusty curmudgeon, Bones," Jim says, toweling his head dry with a borrowed-without-permission towel (McCoy's only towel), post-non-sonics shower. "And I hate to tell you, but when you're on that starship, military rotation's not going to give you enough time to scrub-a-dub-dub out one mini-McCoy in a standing-tub, you know. Sonics, on the other hand..."
McCoy scowls (at the borrowed towel, at Jim, at the terrible joke, at Jim's self-smug grin). It doesn't help that he's been trying to (unsuccessfully) get the damn outdated in-room replicator working enough to get him coffee to survive both this day and make it through this conversation.
Scrubbing a hand up his face, McCoy glares at him and then again at the blinking ERROR message. "Sometimes, Jim, I wonder why I chose you to throw up on." He really doesn't mean it, except he half-way does.
"And like I said before," Jim says easily enough, getting closer with one hand on McCoy's shoulder, completely okay with McCoy's stink-eye, "in spite of everything, I like to think we work out pretty well."
Jim leans into McCoy likes it's completely natural to be so tactile, and reaches out to the replicator. Whatever the kid's doing, in three seconds he's worked out some kind of magic and manages to procure a full cup of McCoy's second poison of choice, and smells entirely too nice to be using McCoy's southern flare of no-scent bar. Leaves a man to suspect he really has brought his own toiletries, and has just chosen not to tell him.
"Don't patronize me," McCoy says, grabbing the cup before Jim can offer it, to swallow a huge mouthful down and grimace at the taste. Room replicator coffee is shit, but it's better than any of the unknown chemicals they're pouring down into the glop that passes as Academy lunches. "I know what you did to get your name on the room, and I'm not happy about you kicking out my roommate to do it."
"You're blaming me about that now?" Jim makes a face at him, sliding the towel off from his head to his shoulders. The smell of McCoy's own shampoo wafts back at him, and it shouldn't make McCoy less sour. "C'mon. Don't act like you liked him either, Bones. He was a dick. What's a little name-change in the system here and there?"
"It-" It doesn't matter anymore, McCoy supposes. He's hot-air at this point, and blows it out with a grumble. "Just go brush your teeth, kid." Jim opens his mouth and points to the replicator. "No, gargling water you diluted a salt pack in does not count." Jim closes his mouth and doesn't move, and even shifts on his feet in an uncharacteristic show of unsureness. "What?"
"Well," Jim says defensively, "I couldn't find your spare toothbrush-"
"What spare toothbrush?"
Jim, bless whatever is going on in his head, looks absolutely floored. "You know...a second toothbrush?"
"Why would I have a second toothbrush? You didn't bring one yourself?" McCoy's a doctor, not a dentist. Like most, he buys a toothbrush when it's time to replace it, and swishes mouthwash daily. A cold, temptful comfort, when you're trying to keep yourself from boozing it up in the day because the ex-wife forwards the upset daughter's letter. "You want me to check if you have some sort of old twenty-second century gum disease from not brushing while I'm at it?"
Jim meanders back into the washroom, fussing with the open cabinets and ignoring the question. "You never have someone staying over? One night stands?"
It's too casual to be that casual, and it's also been all of a week since they flew in from Riverside, Iowa to the Academy.
McCoy has to take a second to process the fact that he is dealing with a man with a hidden possessive streak as passive-aggressive as his daughter's. "It really isn't your bu-put that down."
"Put what down?" Jim asks, too casually, and tries to step so his shoulders will hide his crime like the fast-thinking two-year-old he probably was two decades ago.
McCoy storms over. "You're not using my toothbrush. Gum bleeding on that is a one-way ticket to hepatitis, and oral bacteria can spread faster than herpes. I've got three papers with your name on it, so don't make me refer you."
"But I need to brush my teeth, Doctor Bones," Jim breezes, still holding it up, waving it out of arm's reach. McCoy refuses to play this barely-a-height-game, but there's a huge pile of toothpaste on the bristles. God forbid. You only need a little. "We've kissed. Why can't we share a toothbrush too?"
McCoy is beginning to regret ever resuscitating him from that bar fight three days ago, because it seems Jim thinks he can solve all problems with outmaneuvering common sense with his own logic. "Were you not listening to me when I told you about the dangers of gum and germ exposure? Hell, even giving you mouth-to-mouth then was russian roulette."
"I'm trying not to get cavities here, not contribute to your scientifically backed-up paranoia," Jim complains, and then yelps when McCoy snatches it away and shoves it in his Academy-sanctioned section of the bathroom cabinet. "Bones. Are- Are you seriously biometric locking your toothbrush from me?"
"Use your finger," McCoy snaps. "And buy yourself a toothbrush after class."
At the end of the day, when McCoy returns to the dorms, it's clear Jim's bought a whole pack of toothbrushes that look exactly like McCoy's own, and has stuffed them all in McCoy's half of the bathroom cabinet out of utter spite. He knows this, because when he opens the bathroom cabinet to get to his own, packages of sealed up toothbrushes spill out and drop into the sink when he opens it. Several even drop on his weary head.
"Welcome home," Jim calls cheerily from where he was sitting in bedroom, quietly brushing away, and pads on over to help McCoy clear out the toothbrushes from the sink. He spits out the toothpaste down the drain, rinses, and then gives McCoy a big grin. "Did I pass the roommate test yet?"
"Take a shower," McCoy says, pushing him aside (fondly), "and then we'll talk."