Some complex rules in the official Klingon language exist only because Christopher Lloyd mispronounced a line. Instead of a retake, linguist Marc Okrand integrated the "mistake" into the language's grammar as a contraction. World-Building & Legacy
Nimoy transitioned from actor to director for this film, a role he reportedly secured by informing the studio he would not return as Spock otherwise. This established a major franchise tradition of cast members directing their own series or films. Star Trek III - Alla ricerca di Spock
To prevent spoilers regarding Spock's return, the production used the codename "Nacluv" —which is "Vulcan" spelled backward. Some complex rules in the official Klingon language