The villians of the film were originally intended to be Romulans, but upper studio management wanted Klingons to be used since they were better-known enemies. By the time the decision was made, the Romulan ship was already made and they didn't want the expense of replacing it. Fortunately, the TV show had already established that the Klingons and Romulans had shared technologies and ships in the past (for exactly the same real-world cost-cutting reasons) so the idea of Klingons using a Romulan-style vessel was not a problem.
As explained by William Shatner on "Star Trek: The 25th Anniversary Special" (1991), there was tight security on the set to minimize theft, as incurred on "Trek II". Picture i.d. badges, codes and the works were used so much that Shatner quipped it was like Paramount's real-life "Mission: Impossible".
Contributed by: Robert Baum
Initially George Takei
wasn't keen on being referred to as tiny by the Starfleet guard though director Leonard Nimoy convinced him that the line wasn't meant to be taken as derisive and Takei was satisfied.
When Scotty is leaving the USS Excelsior the voice that says "What level please?"..."Thank You" is that of director Leonard Nimoy
Production was endangered by the great fire at Paramount. William Shatner
helped fight the fire and rescue a crewmember before firefighter reinforcements arrived.
Contributed by: LoverswithCassie
The voice of the flight recorder is that of scriptwriter Harve Bennett
When movies are made, scenes are often
left on the cutting room floor.
Sometimes, there will be several versions
of a movie floating about on cable, tv or video etc. Other times, a Director may
release a special cut of the movie.