We’ve covered before the disappointment expressed by fans of having that five-year mission curtailed and production limbo of the first cinematic adaptation of the franchise and now courtesy of Miss Cellania and Damn Interesting we learn that what became Star Trek: The Motion Picture was primarily reworking of material developed for a planned televised revival series, drawing on the popularity of the original show in syndication and cast members on the convention circuit that arose in the early 1970s not long after cancellation.
Although Spock was not to return for the continuing voyages as a regular character, most of the main crew did with a few additions, first officer Will Decker, Deltan navigator Ilia and Vulcan science officer Xon and scripts and storyboards for at least nineteen episodes were drafted though to never go into production. Some narratives fed directly into the movie’s plot and premises were rewritten for TNG, but many with elements of impostor infiltration and time-travel throughout were never developed further—including a dangerous, covert bit of shuttle diplomacy to the Klingon homeworld to negotiate with the child emperor in order to avert galactic war. Much more about each episode and their writing teams at the link up top, including a conceptual arc from Jerome Bixby, science-fiction author with Star Trek and Twilight Zone teleplays to his credit.