Gene Roddenberry’s logline for “Charlie X” was included in the original “Star Trek Is…” pitch document as “The Day Charlie Became God.” When the series moved into production, Roddenberry gave D.C. Fontana the chance to write the teleplay. That one sentence summary — “The accidental occurrence of infinite power to do all things, in the hands of a very finite man.” — was enough to get the Great Bird a “Story By” credit, even if he cribbed the basic idea from a Jerome Bixby short story “It’s A Good Life,” which had been produced as a Twilight Zone episode a few years before. Interestingly, Bixby himself would later write a number of Trek scripts, including “Mirror, Mirror” and “Day of the Dove.”
As the 8th episode produced (and with a screenplay that underwent very few revisions), “Charlie X” shows the work of a cast and crew that are becoming comfortable with one another, even as they’re introducing new elements, some of which would stick (Uhura’s singing) and others that would be forgotten (the gymnasium sequence, featuring an array of stock footage shot for later use that never happened and the maintenance grates in the floor that vanished soon after). There’s even the first (off-screen) appearance of the ship’s chef, voiced by Roddenberry himself in his only acting role of the series, helping create the illusion that the Enterprise wasn’t just a sound stage in Los Angeles, but a living environment. That was especially important in an episode like this, which was one of only six to take place entirely onboard the ship.
(A lot of praise for that feel should also go to Jerry Finnerman, who lit the set with colored background lights to create atmosphere and warmth on the cool gray walls of the ship’s interior. This practice, which would fade as the series continued, was at the behest of NBC’s parent company RCA, who made color televisions and wanted to use Star Trek as a selling tool.)
While the sexism and weird patriarchal tone of a lot of the episode is a bit grating in the 21st century, it’s also important to note how good Robert Walker’s performance as Charlie is, especially playing against a cast that had been gelling so well. A method actor in his twenties with a youthful appearance, Walker spent very little time off-set with any members of the cast in an effort to help bolster the alienation his character is supposed to feel. In her autobiography, Grace Lee Whitney goes into some detail about this:
"He explained to us when he arrived to the set that he wanted to remain alien and apart from us - and it worked. You can see it in his performance, a subtle yet persistent air of estrangement from the Enterprise crew, and indeed from the rest of humanity. His careful effort to stay in character added a convincing dimension to his performance."
Speaking of Whitney, I’ve always liked her performance in this episode, because she seems to genuinely care about Charlie, even with his unwanted affections become more and more dangerous. Her efforts to deflect Charlie’s advances with the attractive (and age-appropriate) Yeoman Lawton seem less desperate and more matriarchal and her interaction with the captain and other crew members makes it apparent that there was more to her than just handing over clipboards and sighing. It’s a shame she wasn’t able to continue with the series, as it seemed that the directors and writers were seeing something in her. (Of course, this is one of two episodes from her 12-episode run in which she is threatened by someone in her quarters, so.)
"Charlie X" isn’t one of the greats, but it still serves a very solid example of early Trek, with great character work and a plot that ticks right along.