What I thought of the episode when I revisited it sometime ago:
"Spock's Brain" **
An alien steals Spock's Brain and Kirk races against time to retrieve it.
No matter how you try to describe this episode it's going to sound absurd. That said it would have helped significantly if they had started with a better title. Even something as plain as "The Controller" would have been a huge improvement.
What gets me is I think there is a really interesting science fiction story at the heart of this: a living mind needed to maintain a functioning society. And there are some pretty creepy moments in it as well. But it's mostly undermined by poor choice in story elements.
For one thing was it really necessary to have Spock's body brought along like some mechanized zombie??? In James Blish's adaptation I recall Spock's body being left aboard ship until the surgery was ready to proceed. As is it comes across as too absurd. Also was it really necessary to have the Morg women be total airheads??? A little nuance would have worked wonders here. But the last bloody straw was having Spock speak and direct McCoy through completion of the surgery.
And then to end the whole thing with a cheap laugh. Gimme a freakin' break!
Most of the episode is played straight with few missteps, but every so often one of the aforementioned absurdities would ruin what had been accomplished up to that point. It's really hard to accept that Gene Coon could turn in such a botched effort in writing this.
I'd like to add that I quite liked the design of the alien ship. Sadly, instead of enhancing the original retro design, TOS-R felt the need to change it completely for something more contemporary.
I like the story idea, but I'm disappointed with aspects of its execution. And all I can add is that as disappointing as it is I like it better than "And The Children Shall Lead."
Episodes as bad as "Spock's Brain:"
“A Piece Of The Action”
“The Mark Of Gideon”
Episodes worse than "Spock's Brain:"
“And The Children Shall Lead”
“Wink Of An Eye”
“Whom Gods Destroy”