The Star Trek franchise is more popular than it has ever been, but many don't know that The Original Series actually had two pilot episodes. Starting with the unaired pilot "The Cage" in 1965, TOS had a long road to the small screen that involved shooting an entirely new pilot episode that saw most of the cast completely replaced. Though this hiccup seemed to spell doom for the sci-fi experiment, it was actually proof that the concepts devised by Gene Roddenberry had the strength to stand the test of time and were worth the investment in an unprecedented second chance pilot.
Pilot episodes in the 1960s were crucial for the success of a series, and they were presented to executives as a full-length proof of concept that a show could work. "The Cage" was Roddenberry's first attempt to present the world of Star Trek, but it had a TOS as fans actually got to see it in 1966. "Where No Man Has Gone Before" was Roddenberry's second chance with Star Trek, and it would be the pilot that eventually got the show to air. Though they were fundamentally different in execution, both pilots helped establish the various themes of Star Trek going forward.
"The Cage" Was Rejected For Being "Too Cerebral"
1960s television was obsessed with action-packed westerns like Gunsmoke and Have Gun Will Travel, and "The Cage" lacked the "western-in-space" energy that had been promised to executives. As a result, the original pilot was given the ax for being "too cerebral" (via The Star Trek Compendium). Conversely, the second pilot "Where No Man Has Gone Before" introduced Star Trek's first villain and had all the violent chills and thrills that executives wanted. In an introduction to the unaired pilot, Roddenberry stated he saw "The Cage" as an opportunity to do something new with TV sci-fi, but wasn't surprised that it failed.
Despite the failure to deliver the first time around, the executives were clearly still high on Roddenberry's vision and the greenlight to produce a second pilot was practically unheard of in that day and age. "Where No Man Has Gone Before" replaced Captain Pike with Captain Kirk, and it was in the gung-ho captain that Star Trek finally got the "cowboy diplomacy" that blended Roddenberry's utopian vision with the executives' desire for western-like action. Unfortunately, the changes between pilots reinforced things like Captain Pike's insult toward his female crew as the groundbreaking female character of Number One was completely excised from the story.
Star Trek's Second Pilot Proved A Franchise Could Work
TOS' two pilots might have been diametrically opposed in execution and tone, but there was an unintentional consequence for the eventual integration of "The Cage" into the two-part episode "The Menagerie" in season 1. That cost-saving measure actually introduced the idea of a larger world outside the events of TOS and created history for the burgeoning franchise that strengthened it going forward. Later shows like Star Trek: The Next Generation also had an entirely new cast of characters and tone, but "The Cage" had already blazed that trail with Star Trek coming out on the other side a better show because of it.