Alternate Character Interpretation: There's a faction of Star Trek fandom, particularly in Star Trek Online's playerbase, that views the destruction of Praxis as a missed opportunity for the Federation to deal with the Klingons permanently, that they should have taken the opportunity to launch a full-scale invasion because the peace, however well-intentioned, would not prove sustainable: "Yesterday's Enterprise" shows the Klingons and Federation at war despite the Khitomer Accords, with this only averted in the prime timeline through the loss of the Enterprise-C against their mutual foe the Romulans. In 2372 the Klingons go off half-cocked against the newly democratic Cardassian Union, eventually driving them right into the hands of the Dominion, and declaring war on the Federation when their allies try to rein them in. The exact same thing as in 2372 happens in the backstory to Star Trek Online, only with the Undine instead of the Dominion as bogeyman du jour. In both of the latter two instances, the alliance was only restored by a mutual enemy. So what happens when the Federation runs out of mutual foes they can distract the Klingons with? But hey, we got an end-of-the-Cold War allegory out of it, right? And as with the collapse of the Soviet Union, it didn't take so very long for the Klingon "allies" to fall back into their old habits. Exhibit A: Vladimir Putin.
Not to mention that, by DS9's time, we're talking 70-80 years of peace between the Federation and the Klingons, which isn't a bad run at all. Who's to say that a Federation conquest of the Klingon Empire wouldn't have resulted in something much darker by the mid-24th century?
Notably, one of those who had a serious problem with the script was Gene Roddenberry himself. He was particularly disturbed by the more militaristic scenes and treating Kirk's history distrust of Klingons as racism; the original series clearly used the Klingons as "alien Russians" who were guilty of serious ongoing violations of human rights, and he was disgusted with the main plot being defending them through military action without answering for those crimes - he especially disapproved of how the death of David Marcus was used. Luckily for Paramount, Roddenberry died two days after the movie was screened for him, before his lawyer could present his demands to the studio.
Starfleet's decision to decommission the Enterprise-A at the end of the movie. Was it because the Enterprise was simply too old to be worth repairing, as was the case of the original at the beginning of The Search for Spock, or was it a vindictive punishment for all of crew's shenanigans in this movie? Kirk offhandedly mentioned earlier in the movie that the crew was due to stand down in six months, but whether this meant the Enterprise-A itself was already set for decommissioning and it's just being done early is unclear.
Better on DVD: When you watch the film again, you can see just when Spock slaps the patch on Kirk—and see the patch, too. The Klingons weren't very thorough, huh? Or perhaps just didn't recognize it as important?
The film was written at the latest early in 1991 (to give time for filming and post-production for the December release date). The film was essentially about a dual coup attempt against both the Klingons and the Federation so that Blood Knight elements in both could continue their war. In August 1991, there was a coup attempt against Gorbachev in the USSR, by Blood Knight elements in the CPSU who wanted to continue the Cold War.
Hilarious in Hindsight: The Klingon Assassin is actually Starfleet's Colonel West. Rene Auberjonois, who played West, would also appear disguised as a Klingon in the Star Trek: Deep Space Nine episode "Apocalypse Rising". Amusingly, his characters have opposing motivations: West was trying to start a war between the Klingons and the Federation, Odo was trying to stop the Klingon/Federation War going on at that point in the series.
Ho Yay: Kirk and Spock are in the same film, of course there is. There's one particular scene in a corridor that's a deep breath away from being a kiss.
Life Imitates Art: The plot of the film, whereby hardliners attempt a coup against the moderate leader in the hostile empire, was nearly repeated as the film was being edited, in the form of the August coup against Mikhail Gorbachev, on whom Gorkon was based, by hardliners who wanted to go back to the good old Cold War days.
Memetic Mutation: "Only Nixon could go to China" gets used frequently in political discussions.
This is Older Than They Think. The phrase has been in use since at least 1971, before Nixon actually went to China.
Nightmare Fuel: Spock's reaction to Valeris's betrayal. It's chilling to think of how furious he must be to display that much emotion.
One-Scene Wonder: Christian Slater has a cameo as the crewman who wakes Sulu up in the middle of the night. The scene was originally written for Grace Lee Whitney as Janice Rand; Slater only got the part as a favor to his mother, the casting director. Also a case of Promoted Fanboy.
When Chang's Lieutenant or Weapons Officer presses the button to fire torpedoes (installed in a box attached to a wall) you can clearly see the entire box shift position as if poorly glued down.
When Chang is quoting Shakespeare as he watches the Enterprise fly past, the Enterprise looks like what it is: a model, right down to the scored detail lines and paint job. Especially jarring when compared to the other exterior shots of the ship in the movie.
Not all the exterior shots, in fact not many of them at all. This film's visuals of the Enterprise are completely different in style altogether to the other movies, and suffer by comparison. Despite using the same filming model. Especially rubbish is the "warp to camera shot" after Kirk says, "Come on, I need you," to Spock.
There was also no background in the Bird-of-Prey's view of the Enterprise, either, just a completely black space devoid of stars.
The Klingon blood is depicted with early 1990s CGI in all of its imperfect glory. To be fair, it's been twenty years and the technique has yet to be perfected.
It's interesting to compare the blood effects in this film with "Barge of the Dead", an episode of Star Trek: Voyager which aired only 8 years later, to see how much CGI blood (and indeed, CGI liquids in general) had been improved.
The Zero-G blood drops were also one of the first uses of an at-the-time new CGI technology called "metaballs"—a new way to make smooth, blobby, and more organic objects. As much a tech demo proof-of-concept for the technology as a special effect.
The Untwist: General Chang was behind the attack on Gorkon's ship. Given his attitude when he's first seen coupled with the fact that he had the recording of Kirk's statement he would never forgive Klingons, it's not much of a surprise.
Chang is clearly the obvious villain of the piece, though—covering for the real twist in the film that Starfleet officers are part of a conspiracy, and that they supplied Chang with the damning recording of Kirk.