USS Invincible had been known for many years as one of the
happiest ships in the fleet.  There were many reasons for this, but in
large part it was attributable to a number of ship's traditions that
served as both morale-boosters and anchors for a strong esprit de corps.
There was Movie Night, of course, and Taco Night (much imitated
throughout the fleet), and the annual talent show, and the shuttlecraft
races, and the Science! Fair.  But of all of them, the one that was by
far the most popular with the widest selection of the crew, and with
almost as many -practical- benefits to the running of the ship, was the
more-or-less-monthly event officially described on the schedule of
activities as Command Self-Defense Instruction and Demonstration (Open),
better known to the crew as Captain-Pummelling Day.
        On Captain-Pummelling Day, the captain would repair to the
ship's gymnasium at four bells in the first dogwatch, and for the next
two bells he would provide practical demonstrations of self-defense and
close-quarter combat techniques against any member of the crew who cared
to try him.  The opportunities for informal redress of grievance, within
limits, were understood and often cheerfully taken up.  All of this was
not, strictly speaking, in accordance with Starfleet regulations, but it
was a hugely popular occasion nonetheless.