It’s the one where they save the whales! Time travel, McCoy snarking 20th-century medicine, Sarek and a Klingon ambassador arguing, Spock failing his saving throw versus foul language, the USS Enterprise (but not the one we usually see on screen), George and Gracie, “Everybody remember where we parked,” and so much more. The TOS Rewatch does the time warp again and parties like it’s 1986 with Star Trek IV: The Voyage Home.
It’s best remembered as the “save the whales” movie, and the overriding message is a very important one, as sledgehammery as the script has it be. Luckily, things are better now than they were thirty years ago, as humpback whales went from being classified as endangered in 1986 to being upgraded to vulnerable in 1996 and least concern in 2008. The movie’s prediction of a 21st-century extinction for the species is looking less likely. I, for one, am grateful to see that Trek‘s track record for predicting the immediate future remains dreadful (viz. the lack of any Eugenics Wars in the 1990s), as I really don’t want to live to see World War III and the post-atomic horror, thank you very much.