Probably about 20 years ago someone told me about a minor blooper that made it past editing and into the show. To the best of my recollection- McCoy is standing near two characters having a conversation (I assume Kirk and Spock.) He's holding some sort of little doohickey, and he accidentally drops it. He looks around and sees that nobody seemed to notice, then reaches down and picks it up.
I recently bought the OS on blu-ray and got a few episodes into season 3 before I remembered I wanted to look for this. Anyone know which episode it's from? Thanks.