Back to the Future Part III (PG)
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This came out in 1990, just six months after Part II. And like the second movie, I have a vague notion that I might have seen it in the theater, but I'm not sure. And in 1991, there was an animated series which was set shortly after this movie. I want to mention that while the soundtrack from the first movie was totally awesome (a couple of songs by Huey Lewis are most memorable, but the other stuff was all good, too), the second movie didn't have anything particularly memorable. But this movie at least had Doubleback, by ZZ Top, who also make an appearance as a band in 1885.

So... at the end of the second movie, the Doc Brown of 1985 and Marty were both in 1955. Doc Brown and the DeLorean got struck by lightning, and wound up in 1885. Doc later wrote a letter to Marty, which he received right after he'd seen Doc disappear. Then Marty went to tell the Doc Brown of 1955 that he needed his help again, right after that Doc watched Marty and the DeLorean disappear as they did at the end of the first movie. And then Doc fainted. The third movie shows that scene again, then shows Marty taking Doc home. In the morning, Doc wakes up, not remembering what happened the night before, but Marty reminds him. Doc Brown reads the letter his future self had written to Marty in 1885, which tells them where to find the DeLorean, which he'd hidden in a mine. In the DeLorean there were instructions to repair it, as it had been damaged by the lightning, and the parts necessary to fix it hadn't been invented yet... but they would have been invented a few years before 1955. The letter also instructed Marty to take the DeLorean back to 1985 and destroy it, without going back to the past to get the Doc. However, before he can make the return trip, he finds Doc's tombstone, which says he had been killed by Buford Tannen about a week after he wrote the letter. So of course Marty decides to go to 1885 and save the Doc.

When he arrives in the past, the car's fuel line gets shot by an arrow, and loses all its gas. This is a problem, because of course there are no gas stations in 1885. But Marty finds Doc, who is working as a blacksmith, and they make plans on how to get back to their own time. They ultimately decide they'll need to hijack a train to push the DeLorean. But they run into a few complications. For one thing, Buford takes a disliking to Marty (who calls himself Clint Eastwood while in the past), and challenges him to a gunfight a few days hence (on the very morning Doc originally would have died). But before that can happen, Doc meets a schoolteacher named Clara Clayton (Mary Steenburgen), and they fall in love at first sight. (Which Doc had previously said could never happen to him, since it's not scientifically possible. I tend to agree with him on that point, though I'm always willing to suspend disbelief for the sake of a story. And while I've always thought he was much too old for Clara, I must admit their personalities were nicely compatible. She's always liked science, and they're both fans of Jules Verne.) Oh, I should also mention that Marty met a couple of his own ancestors, Seamus and Maggie McFly. (They're played by Michael J. Fox and Lea Thompson, which seems kind of weird... I mean, I get Marty looking like his ancestor, but the fact that Marty's mother looks like Marty's ancestor is kind of disturbing. I may have read something years ago that explained that, like the notion that men marry women who look like their mother, so maybe George McFly's mother just happened to look like Lorraine Baines. Of course, this would have to have happened for every generation going back to Seamus, considering each generation could only get the surname "McFly" from the father. I find that idea kind of disturbing, but at least not as disturbing as a different explanation would be.)

Anyway... I don't really want to say any more about the plot, except that there's a happy ending, not just for the movie itself, but for the entire trilogy. (But then again, as I said, there is a spinoff cartoon, which may or may not be canonical. So it's not necessarily the end.) As with the second movie, the third also has running gags that started in the first movie, which I think mostly work... though there's one joke that I thought really didn't make sense to have repeated. (Why did 1955 Doc not remember Marty telling him in the first movie that "all the best stuff comes from Japan"?) But that's not important. And um... there are several new jokes. And... something that was set up in Part II paid off at the end of Part III. And I dunno what else to say, except it's just a really fun movie. (Oh yeah, and just like the Twin Pines Mall becoming the Lone Pine Mall in the first movie, there's a nice visual touch about a certain ravine having a new name, when Marty finally gets back to 1985 in this movie.)