Although not mentioned on-screen, the novelization establishes that Saavik was half-Vulcan and half-Romulan. A scene cut from the previous film Star Trek II: The Wrath of Khan (1982) (where Saavik was played by Kirstie Alley) also established this but can not be considered canon. Leonard Nimoy seemed to have directed Robin Curtis to portray Saavik as a full Vulcan.
The villains 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 built and they did not want the expense of replacing it. However, since the original Star Trek (1966) series 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), the idea of Klingons using a Romulan-style vessel was not a problem.
When Admiral Kirk toasts with his officers, he raises his glass to "Absent friends". In the Royal Navy, toasts were given by the officer in charge based on the day of the week. Absent Friends was a toast given when raising the glass on a Sunday.
When the Enterprise enters space dock at the beginning of the movie, just before Uhura comments on the Excelsior's appearance ("Would you look at that!"), another docked ship can be seen, in shadow, at the upper left corner of the screen. This ship is one of the alternative models that was considered for use as the Excelsior. This alternate model also makes several appearances in Star Trek: The Next Generation (1987), usually as a wrecked ship or piece of space junk.
The shot of the Enterprise approaching Spacedock is later reused in various episodes of Star Trek: The Next Generation (1987) with the Enterprise-D overlapping the original Enterprise (Another cost-saving method often used with Star Trek (1966)).
It was director/star Leonard Nimoy who conceived the distinctive design of the Klingons' Bird-of-Prey. At a preproduction meeting with Industrial Light & Magic (ILM), Nimoy posed his arms and hands to demonstrate the vessel's wings as they ultimately would appear in the final film. The DVD documentary "Space Docks and Birds-of-Prey" revealed that the physique of a bodybuilder in the "crab" pose, emphasizing the trapezius muscles, was also the basis for the ship's aggressive stance. Finally, the script, at the time when it was received by ILM, established that the Bird-of-Prey was definitely a Romulan vessel, commandeered by Kruge. With that back story in mind, the feather-like pattern on the ship's underside was a direct tribute the original Bird-of-Prey as it first appeared in Star Trek: Balance of Terror (1966). Though the final version of Star Trek III (and subsequent Star Trek films and television episodes) refer to the ship as purely of the Klingon fleet, the Romulan plumage-detail was never lost.
Production was endangered by the great fire at Paramount. William Shatner helped fight the fire and rescue a crewmember before firefighter reinforcements arrived. Shatner said that his motivation for doing so was purely to save a day on the shooting schedule, as he had a make a deadline to be available for shooting on a new season of T.J. Hooker (1982).
When Kirk meets Admiral Morrow for a drink to discuss taking the Enterprise back to the Genesis Planet, an abstract hanging sculpture can be seen on the wall behind Morrow. The sculpture is in fact one of the miniatures of the Epsilon IX station from Star Trek: The Motion Picture (1979), which was made of acid-etched brass.
George Takei initially expressed reservations regarding the scene where the security guard called Sulu "Tiny". While Takei liked the scene overall, he felt that Sulu being called "Tiny" didn't make much sense, even when Harve Bennett explained it was due more to the large size of the Security Guard. When Takei first saw the film with an audience of fans, he came to recognize the scene (and Sulu's line "Don't call me Tiny") as a real crowd pleaser, which changed his outlook to a positive reaction.
The bridge of the Bird-of-Prey was originally constructed for a different science fiction film that was started but never finished. The producers of this film used it in an effort to save time and money.
As in the previous Star Trek film (Star Trek II: The Wrath of Khan (1982)), the movie includes the famous "Space, the final frontier" monologue, spoken by Spock. As in the previous film, the words have been changed slightly, referring to seeking out "new life forms" instead of just "new life". This was the final use of this modified version of the monologue.
The few Klingon phrases that Mark Lenard introduced in Star Trek: The Motion Picture (1979) was used by Marc Okrand as the basis for the Klingon language in this film. Okrand's Klingon language became a fully realized fictional language, and would be the basis for all future Klingon dialogue in future movies and television series (as well as an obsession to become fluent in for hardcore Star Trek fans).
This film marks the first appearances of the Excelsior-class vessel, the Oberth-class vessel (namely the USS Grissom), and the Klingon Bird-of-Prey. The models were reused as other, similar ships in numerous episodes of Star Trek: The Next Generation (1987) and Star Trek: Deep Space Nine (1993).
Christopher Lloyd, who played the Klingon Commander Kruge, also played Jim Ignatowski on the situation comedy Taxi (1978). In one particular episode, a television executive is in his cab and Jim says he loved the series Star Trek (1966). Jim added that he didn't like the leader of the Klingons because the writers had him say things a "real Klingon just wouldn't say."
Dame Judith Anderson was 87 years old when she appeared as the High Priestess in this film. She had come out of retirement after being away from motion pictures for 14 years. She was encouraged to take this part by her nephew. This film was also her final on-screen feature film appearance, although she did have a voice acting part two years after this film, but did not actually appear on screen.
When negotiating Kirstie Alley's contract for Star Trek II: The Wrath of Khan (1982), Paramount did not offer or include any options or clauses regarding any possible sequels. According to Leonard Nimoy, this left Alley open to negotiate a new contract for Star Trek III, resulting in Alley's excessive salary demands which led her to being replaced by Robin Curtis.
The uniforms worn by the security guards are the same uniforms from Star Trek: The Motion Picture (1979), but they're worn with the new red Starfleet uniforms, and a dark green turtleneck, which represents the security division.
When the crew is standing on the bluff supposedly watching the flaming Enterprise hulk, they were in fact watching a tennis ball mounted on an overhead boom microphone. The shot had to taken many times because not everyone was watching it at the same time.
Dr. McCoy says he would be more comfortable giving Spock one of his kidneys, than carrying around Spock's soul in his own mind. In Star Trek IV: The Voyage Home (1986), McCoy gives an elderly woman a pill that causes a new kidney to grow--so if McCoy had donated one, it wouldn't have been a big loss!
Studio Chief Michael Eisner resisted the idea of Leonard Nimoy directing because he mistakenly thought that the reason for Spock's death stemmed from a hatred that Nimoy had about Star Trek. However, this was not true because Nimoy jumped at the chance to direct when the original director Nicholas Meyer turned it down.
Robin Curtis was instructed that when she got home every night after shooting that she was to put antibiotics on her ears so that the chemicals used to keep her pointed ears glued on wouldn't cause skin problems.
In the original script, after T'Lar warns McCoy about the dangers of fal-tor-pan, McCoy says "I accept". Dame Judith Anderson suggested to producer Harve Bennett that they should add the word "danger" because it would heighten the drama.
Grace Lee Whitney:
Janice Rand, Kirk's yeoman in season one of Star Trek (1966) and returned as transporter chief in Star Trek: The Motion Picture (1979), makes a cameo appearance during the Enterprise's docking sequence. She is the red haired officer in the spacedock lounge who shakes her head in disapproval as she sees the ship's damage.
The trivia items below may give away important plot points.
Close to the end of the film, after landing on Vulcan. While Spock's body is being carried up the long staircase to begin the fal-tor-pan ritual, the "maidens" carrying Spock are not actually touching him. They are actually holding their hands above him, effectively levitating his body to the altar.
The chirping on the tricorder (especially when Sulu scans after the Enterprise is destroyed) comes from an audio remote control device for the Radio Shack ("Realistic" label) answering machine. The remote control was able to be used away from home, over the phone to signal the answering machine (through electronic chirping sounds) to play back massages or carry out other functions.
When Kirk calls out to Kruge, the Klingon commander has his head in his hands. According to the original storyline, Kruge is not mourning the loss of his troops, he's humiliated because Kirk was more cunning than he was. Through Kirk's apparent suicide, Kruge has been beaten and shamed.
The scene in which Kirk stumbles into his chair after hearing of the death of his son was an improvisation by William Shatner, who was told by Leonard Nimoy to do whatever reaction Shatner wanted to do. Shatner has never told whether he meant to miss the chair and slip to the ground, or if he had meant to simply hit the seat hard but missed going backwards.
There was a debate during the writing of the script as to who should be killed by the Klingons - Saavik (Robin Curtis) or David Marcus (Merritt Butrick). It was eventually decided that Marcus should die as punishment for experimenting with protomatter in the Genesis matrix.
Scenes of Spock's final moments and his death from Star Trek II: The Wrath of Khan (1982) were reused as the engine room's flight recorder. The opening death sequence, funeral sequence, Spock's casket's landing spot, Spock's opening dialogue and opening were all reused from Star Trek II where they were all used at the end of that film.
In the earlier drafts of the screenplay, the Enterprise's auto destruct finished with the ship's engine core exploding, resulting in a massive matter/antimatter explosion, visible from the planet's surface. Harve Bennett later changed this to the primary hull exploding, and the secondary being destroyed in the planet's atmosphere, reasoning that an antimatter explosion would probably destroy the Klingon ship as well. However, a mix-up resulted in the ILM crew doing the sequence according to the earlier version. Bennett considered using this version in the final film, but asked ILM to redo it, this time saying it would make the scene afterward look too much like the ending of Star Wars: Episode VI - Return of the Jedi (1983). They saved money by re-using the footage from the initial sequence up to the point where the primary hull exploded, then started the new sequence just after.
Christopher Lloyd, who is most famous for playing Doc Brown, inventor of the time machine in the Back to the Future (1985) trilogy, plays the Klingon commander whose ship is taken over by Kirk and his crew. In the next movie (Star Trek IV: The Voyage Home (1986)), Kirk coincidentally uses this same ship to travel back to the 1980s, near the 1985 date that Brown first used his famous DeLorean time machine.