Chewbacca was not, actually, having a good time.
It was the third bar they'd been to, and Han had been shot down twelve times. Every time a woman told him to fuck off, he got a little whinier, until Chewbacca was ready to hit him over the head and haul him back to the Falcon to sleep it off. Lucky number thirteen, he figured, was going to be the cutoff; Han probably wouldn't be able to tell a hangover from a—well, he wouldn't give him a concussion. Much.
Dean saves the world the same way he entered it: buck naked.
Like a number of other things he’s caught himself doing since enlisting, McCoy takes Tactical Analysis because Jim Kirk asked him to. His argument against it - “I’m a doctor, Jim, not a fucking bridge officer, what the hell do I want to take that for?” - fell on deaf ears.
Jim, he had learned in short order, was scheduled for the Kobayashi Maru. And like a number of other moronic ideas that kid had had since enlisting, he wanted McCoy to do it with him, which meant McCoy had to be enrolled in or have already taken Tactical.