Leonard Nimoy initially refused to return as Spock due to unpaid royalties from the original series, so the character was left out of the screenplay entirely until studio executive Jeffrey Katzenberg flew to New York and, by his own account, got 'on my knees begging' Nimoy to rejoin the film.

Stephen Collins was the only actor personally cast by director Robert Wise, and he landed the role of Decker while being almost completely unfamiliar with the Star Trek franchise, more interested in working with the legendary director than in the part itself.

Persis Khambatta agreed to play Ilia even after Gene Roddenberry warned her she would have to completely shave her head for the role.

James Doohan invented the Klingon vocabulary heard in the film on his own, which linguist Marc Okrand later expanded into a fully developed Klingon language.

The project went through years of false starts, including an abandoned first script called 'The God Thing' by Roddenberry, a rejected treatment by Harlan Ellison, a black-hole story by Robert Silverberg and John D. F. Black, and a nearly-produced version titled 'Planet of the Titans' with production design by Ken Adam and Ralph McQuarrie fresh off Star Wars.

Before becoming a feature film, the story was developed as 'In Thy Image', the pilot for a planned television series called Star Trek: Phase II, which was cancelled just two and a half weeks before production was due to start when Paramount decided to make a feature film instead, laying off cast and crew within the same week they were hired.

The shooting script was in such constant flux that revisions were dated by the hour, and actors were told not to memorize the final third of the screenplay because it kept changing during filming; a final draft of the third act wasn't approved until late September 1978.

The V'Ger set, nicknamed 'the Coliseum' or 'the microwave wok' by the crew, was designed and built in just four and a half weeks, while the massive 68-foot V'Ger model was constructed from the rear forward using materials including wood, foam, macramé, Styrofoam cups, and neon and strobe lights.

The Enterprise engine room set was only 40 feet long but was made to look hundreds of feet long on screen through forced perspective, a slanted and narrowing floor, and the use of small-statured actors as extras to create the illusion of depth.

The only prop retained from the original television series was Uhura's wireless earpiece, which Nichelle Nichols specifically requested on the first day of shooting, after most of the production crew had forgotten about it.

The film's budget ballooned from an initial $15 million to approximately $44 million, and although it earned $139 million worldwide, this fell short of studio expectations, prompting Paramount to demand a cheaper sequel and push Roddenberry out of creative control for Star Trek II: The Wrath of Khan.