Saw an article titled “Why Does Star Trek’s Dr. McCoy Wear a Pinky Ring?“, and thought the accompanying picture was photoshopped as a gag:

I mean, I’ve probably seen every single ST:TOS episode a dozen times in my life and never noticed this before.
But yeah. It’s there.
Here’s a McCoy “Best Of” montage so you can check it yourself. Easier to spot in some places than others, but it’s there.
[Great Bones McCoy Lines Part 1]
Anyway, Neatorama has the story behind it.

Not to brag, but I noticed it all along, but thanks to your link I now know the story behind it.
Parenthetically, Neatorama claims that Buster Keaton never (in italics) smiled on film. He did, early on; it didn’t work comedically; he dropped it. No more accurate than if they said Spock never laughed.
Hmm… I can use that!