One of those flaws presented itself in the show’s first season. In the show’s 25th episode, titled “The Devil in the Dark,” there were no female speaking parts. It was a shift from the show’s norm. Despite having women in the main cast, none appeared, spoke, or were credited in this particular episode, shows IMDb. It originally aired on March 9, 1967, and just a few weeks after its air date, its creator quickly picked up on what was amiss and penned a letter noting the slip-up to one of the show’s writers.
Per Trekkie directory site Memory Alpha, Gene Roddenberry was keenly aware of the error and challenged show screenwriter Gene Coon to be mindful of finding ways to be inclusive and creating instances where women could be employed. He also stated that in moving forward with writing more women into the show, the scenes needed to be logical and not cringeworthy.