I've written a few pieces of fan ficton regarding the "Whom Gods Destroy" episode of Star Trek, which of course starred one of my favorite actors, Steve Ihnat.
They are downloadable as free PDFs here: http://volcanoseven.com/BriefCandle/StarTrek/Garthfanfiction.html
There's a prologue to the episode, called "The Madness of Garth of Izar" which attempts to explain why Garth's madness took the form it took, and then there's Who Goes There? which is a complete re-envisioning of the episode, as it should have been!
To explain some of the in-jokes:
1. The title refers to the John Campbell sci-fi story, Who Goes There?, which in turn was the basis of The Thing From Another World, the great 1950s movie, and The Thing, a 1990s remake with Kurt Russell. In the short story, the alien is able to appear as anybody he wants (or can possess anyone he wants, I forget now, as it has been a long time I'since I've read it, I confess.)
2. All of the male characters - who are not actual Star Trek characters - possess names of characters that Steve Ihnat played during his career. I'd originally intended for Who Goes There? to be much longer, and to take place entirely with the cast of the Enterprise, but for various reasons I changed my mind, so only half of Steve's character names are used...
3. Gus Keller, Garth's ultimate persona, is of course from Mannix: End Game. I echo a few of Gus's lines in the story...as well as a couple of Lt. Minns' lines...
So, I hope you enjoy.