Though it's now one of the seminal science fiction franchises on television, Star Trek initially had a rather rough time in its quest to go where no man had gone before. The show was canceled after a relatively brief three seasons, but its voyage to even getting on the air was a hard-fought battle, too. Gene Roddenberry had to shoot two pilots for the series to finally be picked up, but he wasn't willing to completely do away with the hard work done for the first one. Before it was reimagined as the origins of Pike and Spock's relationship, "The Cage" was meant to be Star Trek's first movie. Here's how Roddenberry first tried to bring the Enterprise to the big screen and why this plan fell apart.
The Cage
"The Cage" was Star Trek's original pilot and was completed in January 1965 only to be rejected the following month. Though it laid the ground for what the franchise became known for, it bore a distinct difference to the eventual pilot. For starters, the resident captain of the series' spaceship wasn't Captain Kirk but Christopher Pike. Leonard Nimoy played Spock, but he was characterized in a more upbeat way than normal and was not the ship's first officer.
The story involved Pike and his crew investigating a distress signal on a planet called Talos IV, where they encountered the survivors of an expedition whose participants had been missing for almost two decades. Also on the planet were the native Talosians, whose psychic illusions were used on Pike and others for incredibly sinister means.
True to the series' eventual identity, NBC characterized the pilot as "cerebral and slow," which wildly contrasted with other sci-fi shows of the time that were essentially Westerns that traded six-shooters for lasers. This pilot was incredibly expensive for its time, costing around $600,000. For the sake of bringing his vision to life and making good on his particularly expensive venture, Star Trek's creator had another idea for what he already shot that eschewed television entirely.
Star Trek: The Motion Picture
Roddenberry planned to reuse the original pilot in another, far more substantial way so that the effort gone into it would not be in vain. This involved turning the episode into a theatrical, feature-length movie that could possibly reach a wider audience than the planned TV show. This would have involved one of two methods: bolstering the pilot's runtime with material that had already been shot but cut for broadcast or simply shooting new material to add.
Both of these ideas came with their own issues. The major problem with the first option was that re-adding material could ruin the flow and pacing of the already "slow" storyline. The second option involved shooting more to add to the story, such as the horrific accident that befell the survivors on Talos IV. The only problem was that Jeffrey Hunter, who played Pike in the failed pilot, was now a bigger name in Hollywood. He was neither affordable nor particularly interested in the project.
The inability to organically add to the story meant that Roddenberry had to put the kibosh on the feature film idea. His plans to make this movie was confirmed by Scotty actor James Doohan and later in the pages of the Inside Star Trek: The Real Story reference book. The original pilot was eventually used as part of Pike and Spock's canon backstory in the two-part story "The Menagerie." The series later revived into a multi-million dollar film franchise, as well. These were all part of the ambition and legacy that Roddenberry imparted in his creation, even if he envisioned achieving these things far sooner than they did.