May be old news on this thread, but I was fascinated to read that Janos Prohaska, who created the Horta costume, showed it to Gene Coon, and when he asked what it was Prohaska said "It can be whatever you want." Apparently Coon replied "I'll write a script around it" and wrote this episode in 4 days. The man was pure genius.
Something I only recently realized-- “The devil in the dark” is us humans, not the Horta.
And one thing that always puzzled me is why Shatner claims this as his favorite episode, when his father died. Nimoy and others helped him through, but still it seems strange.
I had forgotten this story; thanks. Did Coon confirm it?
You're right - the "devil" changes. First it's the unknown assailant, then it's the revealed Horta, then it's the miners, both in the event and in retrospect. It's just an absolutely brilliant story, as you noted. Genius indeed.
I figured Shatner remembered how the show, cast, and crew supported him and he was able to make something enduring that he probably viewed as a tribute to his father. I've read and seen enough of Bill's writings and words that I can comfortably believe that's consistent with his personal outlook. He was and is an amazing hard worker and utterly dedicated to his craft. Being able - with the help of his colleagues - to deal with a sudden devastating loss and have it not interrupt his work or even show on film (on the contrary, this episode is one of his best performances in the entire series) would make Bill, in my speculative opinion, extremely proud and happy for the memory of his dad. Add in the fact that it's a superlative episode and there you have it.