3. Director Nicholas Meyer rewrote the script in only 12 days.
With no workable script, and a release date already targeted, Paramount were in dire straits until executive Karen Moore suggested writer-director Nicholas Meyer, who'd had a recent success with time travel picture "Time After Time." Meyer had never seen an episode of "Star Trek" (later saying that "the chief contribution I brought [to the film] was a healthy disrespect... I tried through irreverence to make them more human and a little less wooden"), but was keen on the idea of tackling the film. He went on to compile a list of highlights from previous drafts, and went on to blast through a new draft in the twelve days needed before work on the effects had to begin, for no pay. Among his most lasting contributions were a more Naval take on Starfleet, inspired by the "Hornblower" novels by C. S. Forester, with redesigned ships and uniforms. Roddenberry didn't approve, but he was way out of the loop at this point. Meyer also turned Spock's protege Saavik into a female character, and, while his first choice was Kim Cattrall (who Meyer would eventually cast on his return to the franchise for "Star Trek VI: The Undiscovered Country"), future "Cheers" star Kirstie Alley wound up in the role.
4. Rumors of Spock's demise led to Leonard Nimoy getting death threats.
Killing off the ever-popular Spock was on the cards from the very beginning: Leonard Nimoy was reluctant to return to the role, and only did so on the condition that his character wouldn't survive the film. In early drafts, Spock was actually killed in the first act (in a move Bennett said was inspired by the death of Janet Leigh in "Psycho"). But despite secrecy, word of the move leaked early, causing a fan outcry: one group of Trekkers paid for an advert in Variety decrying the idea, and Nimoy even got death threats from particularly fervent fans. Nevertheless, the prouduction moved ahead with the plan, albeit moving Spock's demise to the end of the film. However, as production went on, Nimoy found himself enjoying the experience more than he expected, and pressed for the door to be left open for him to return. When the ending tested poorly, it was settled, and the scene where Spock's casket lands on the newly formed planet of Genesis was added, despite objections from Meyer, and plans started to form for a third installment, "The Search for Spock," which Nimoy would direct.
5. The film features the first all CGI-sequence in film history, created by the company that would eventually become Pixar.
Despite the innovations of "Star Wars," computerized special effects were still in their infancy, with models and other techniques still making up the bulk of effects work at ILM, who were the main house working on 'Wrath of Khan.' For instance, the nebula was created with a latex rubber and ammonia mixture being injected into a cloud tank full of fresh and salt water, and shot at two frames per second. But the film did serve as a pioneer by featuring the first entirely CGI sequence -- where the effects of the Genesis Device on a barren planet are developed. LucasFilm's Computer Graphics group were brought on, hoping that it would become a showcase for their work (see the featurette below). They would go on to create the Stained Glass Knight scene in "Young Sherlock Holmes," before Lucas sold the group to Steve Jobs in 1986, when it was renamed... Pixar.