Well, I mean, he was. Nimoy and Kelley played important roles. But Shatner was still the lead.Apparently some of it was Roddenberry telling Freiberger that Shater was the lead and not Nimoy.
Oh I never said Roddenberry was wrong.Well, I mean, he was. Nimoy and Kelley played important roles. But Shatner was still the lead.

The antibodies will have a field day with Chekov.What if the characters had had to miniaturize and enter Spock's brain to reattach it?
But this time it's the wig which drives the antibodies berserk.^People would think, "Wasn't this already done, but with Raquel Welch?"
Agree completely. Now I appreciate it as one of the few third-season episodes that has much of the "fun" energy of the first two seasons (unlike many third-season outings that are talky, plodding, badly directed and downright bleak in tone).The worst episode has always been "And the Children."
...
"Spock's Brain" is a fun but unserious outing, with some chills, some laughs, some cheesecake, some cool shots (rear-screen on the bridge, prop close-ups), and a fantastic music score..."
The 1936-40 Flash Gordon serials, a few slight creaks aside, are great. Just saying.It's as much a product of it's time as the black & white Flash Gordon serials.I love the thing.
Donald Pleasance sabotages everything while Kirk hits on Raquel, but McCoy gets to use a thruster suit inside V'ger/Spock.What if the characters had had to miniaturize and enter Spock's brain to reattach it?
Okay, let's take a crack at this.




Making it Spock's brain that gets removed makes it more understandable that he can survive the operation, having Vulcan anatomy which could have any number of characteristics that Humans don't have, so we can understand it's likely why he manages to live until he can be sustained by tech. Also, the technique is informed by alien tech.
Further, removing Spock from the equation temporarily means the crew believes they have to figure out what happened without his insight to guide them (until they find the machine his brain's connected to). There's a time limit to retrieve him, so the clock's ticking and they're significantly hampered by his mental absence.
Removing anyone else's brain: I suppose the person would be declared dead and a funeral would be held, or perhaps delayed because the crew feels the dead man should be buried with his brain, at the very least. Then when they find there's a chance to restore the dead person, they'd jump at the chance. If it was Kirk, that would leave Spock in command. It couldn't be McCoy's because you'd need another doctor to perform the operation, so a guest star.
One thing this episode does is it requires Spock and McCoy to work together to save Spock's life. They complement each other.
You're not wrong.But that'd be boring. Just like if they made "Space 1999" but focusing the show on everyone on Earth instead of the moonbase**.
** Not that I'm about to editorialize, but:
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