The fourth film in the "Star Trek" franchise, released in 1986. Directed by Leonard Nimoy and written by Nimoy and Harve Bennett.
The stars include:
When Earth is attacked by a deep-space probe, the crew of the Enterprise (currently aboard a Klingon warship after Spock's resurrection in the previous movie) realize that the probe is trying to communicate with Earth whales, which have been extinct for centuries. So the crew hatches a hairbrained scheme to travel back to the 20th century, kidnap some whales, bring them forward to the present, and hope the whales will tell the probe to go away.
A series of misadventures ensue, as the crew tries to get the hang of 20th century San Francisco, track down material to construct a whale tank in the Klingon ship, find a way to repower the ship's batteries, and kidnap some whales -- which they find at an aquarium, guarded by Dr. Gillian Jacobs, a whale researcher frustrated that the whales will soon be released back into the ocean, where they may not be able to survive.
The movie is significantly funnier than any other Trek movie, with lots of wonderful, humorous moments, including Kirk and Spock, who is unusually loopy as he's still recovering from being dead, arguing about whether or not they like Italian food, Scotty speaking into a 20th century computer mouse like it's a microphone, Spock taking out an obnoxious punk with a nerve pinch, McCoy acting horrified by the primitive and barbaric conditions in a modern hospital, and Spock exploring the many uses of profanity.
All in all, it's an extremely fun movie, still one of the best regarded of all the Trek films, and it's still a joy to watch.