Both of the Star Trek pilot episodes had women in long pants. You know it might get cold in space, and without gravity the girls skirts might float up and distract all of the crew men! Grace Lee Whitney requested the uniform change. She was a dance and wanted to show off her legs. She was originally cast as the second in command, or in charge of the ship's female crew members. She had Kirk were to have a subtle attraction that they couldn't act out for the good of the mission. That's how it was sold to the networks. Ultimately, Roddenberry demoted her, likely because she rebuffed his aggressive advances, and managed to get his future wife, Majel Barrett, into the cast, and he also had a side relationship with Nichelle Nichols, who was a divorced mother. (Watching the show in reruns, people miss that Whitney only appeared in the first part of the first season.) Roddenberry's decision to terminate Whitney and Rand's character likely doomed the show since it then lacked a compelling story line for women, and led to the silliness of Kirk's serial affairs with alien women who might not even have human female genitalia. The show could have had a much longer run with Whitney playing Rand. She was beautiful. She went from Star Trek to a few appearances playing a Tutette on Batman.
Sorry if the images are too big, but resizing them is a PITA.