Back to the Future ends with a giant smiley face of Hollywood froth; a playful, open-ended but nonetheless satisfying conclusion that promises our characters will still be around, having their adventures. The endless possibilities inherent in the story of a time-traveling car - which can fly now, thanks so much - created an infinity of unexplored vistas, of which Doc Brown's very off-handed reference to "your kids" was merely the tip of the iceberg. In a modern age of sequels green-lit before the first movie is even out of post-production, the ending would be an obvious, slightly charming, slightly groan-worthy sequel hook, but when they first wrote the screenplay, neither Zemeckis nor Gale had any such notion in mind. That is the most important fact to keep in mind about the Back to the Future trilogy: it was conceived as a simple, standalone comedy.

Of course, the movie industry was the same bastard beast in 1985 as it is now, and after Back to the Future became a gigantic smash, Universal Pictures and Amblin Entertainment couldn't make up the contracts for a sequel quickly enough. It had to wait; Zemeckis was already throwing himself into another Amblin project, Touchstone Pictures' Who Framed Roger Rabbit. It was only after that technically ambitious masterpiece of family filmmaking wrapped principal photography that the director was able to take a peek at Gale's initial scripts for what was still meant to be a single vasty follow-up stretching from the marvels of 2015 to the rugged frontier of 1885. It quickly made sense to divide the story into two parts, which for convenience would be shot in one fell swoop; and thus was franchise history made.

Sequels as such stretch into the silent era; the idea of a trilogy being the ideal franchise model is considerably newer. It was the unprecedented success of Star Wars in 1977 that birthed what has become an excessively common formula: a standalone original would be followed by a middle film that ended on a cliffhanger, so that the "trilogy" could rather be thought of as Film 1 and Films 2+3 (in a "true" trilogy, such as Satyajit Ray's Apu films, or more recently the Sam Raimi Spider-Man franchise, the three parts form a unified whole, but each stand unique and independent). Back to the Future was one of the earliest examples of this format to follow in Star Wars's wake; what made it a trendsetter was the idea that the sequels should be produced right on top of the other, with hardly any break in production or in release dates. The only precedent I can find to this - and my knowledge is hardly definitive - is, arguably, Superman and Superman II, initially meant to be filmed together, until backstage issues put a temporary brake on the second installment. It has become altogether more common: The Matrix and Pirates of the Caribbean trilogies both followed the BttF model almost to the letter, and it takes little imagination to see the same impulse in the megalithic production schedule of the three Lord of the Rings films, or in the mad dash to crank out five Twilight pictures before everybody stops caring about the property.

None of this has very much to do with the film released in November, 1989, as Back to the Future, Part II. Picking up slightly before the original left off, with a re-filmed version of that movie's closing scene providing a new actress in the role of Marty's girlfriend Jennifer (Elisabeth Shue, replacing Claudia Wells), and Doc Brown getting noticeably re-framed dialogue to set up a slightly different scenario than the first film ended on, the new film skips ahead thirty years, to find Marty's son, Marty Jr. (played by Michael J. Fox, just like his old man), getting in some trouble with Griff Tannen (Thomas F. Wilson), the grandson of Marty's 1955 nemesis Biff (ditto). This situation resolves itself fairly quickly, but not before old Biff steals the time machine to go back to 1955 and present his teenage self with a copy of a sports almanac that the young man uses to make himself a billionaire, turning 1985 into a hellish nightmare fantasy. Marty and Doc, protected somehow from the effects of the change - though for how long, it's hard to say - head to 1955 themselves to stop Biff from changing the timeline. Naturally enough, this leads to both of them interacting, in potentially dangerous ways, with the plot of the first movie, and it all ends with Doc being zapped to God knows when during the same lightning storm that sent Marty back to 1985 in the first place.

It says quite a lot about Zemeckis and Gale's continuing strengths as writers that what I just wrote makes absolutely perfect sense while you're watching it. And that all the jerry-rigged elements meant to turn the thin promise of further adventures made at the end of the first movie harmonise rather effortlessly with the original, turning casual gags into clever foreshadowing and building recurring motifs out of one-liners, while also providing a fine story that hangs together and is perfectly effective on its own. Mostly. The filmmakers have been open in later years that if they knew that the final scene of Back to the Future was in fact setting up a sequel, they'd never have put Jennifer in the DeLorean with Marty and Doc, knowing that they had nothing interesting to do with her. Lo and behold, it is very much the Jennifer elements of the plot that feel the most awkwardly kludged in, adding nothing but a handful of minutes of running time.

In the main, though, Part II does exactly what a sequel should do, yet remains a rarity as thrilling as seeing a Siberian tiger in the wild: it faithfully continues the story of the first film without in any significant way repeating it, and it expands upon the rules set up by the first film without violating the spirit of those rules. Or to put it another way: Part II is the film that actually plays around with the ramifications of time travel as established in Back to the Future. The first film is mostly just a fish-out-of-water comedy with some pronounced overtones of Oedipal dread; it's in the second film that we actually start to deal with cause-and-effect, paradox, and a genuinely twisty plot that you really need to focus on. It's also in Part II that we see the franchise's only feints towards one of the classic topics of time-travel fiction: what will the future look like?

Though the 2015 sequence occupies only a portion of the movie, it has usurped nearly all of the popular awareness of it; and not without reason. Knowing that they could never predict a "real" version of the future, Zemeckis and Gale instead created a vision of thirty years hence (or 21, depending on how you're counting) that is unmistakably meant to be the future if the '80s just keep going on for three straight decades. Surely by accident, this '80s-centric vision of the 2010s has proven to be one of their most spot-on predictions (not the fashion, maybe, but have you looked at pop culture lately?) - the only keener observation is the movie theater with the abnormally intrusive advertisement for Jaws 19, a tawdry 3-D epic. It's depressingly likely that 2015 might see a gaudy 3-D version of Jaws (update: this did not happen, thank the good Lord), though it would be a remake, not a sequel; probably directed by Marcus Nispel, with Bradley Cooper as Brody, a playfully slumming Ewan MacGregor as Quint, and Amanda Seyfried as "Mattie" Hooper. Um... oh, yes, Back to the Future, Part II.

It's in 2015 that most of the whiz-bang awesomeness of the movie is found, not just in the staggeringly over-detailed production design by Rick Carter - hardly a single frame of this sequence doesn't have some coy detail about life In The Future snuggled away where you simply won't see it without a pause button handy - but in Zemeckis's embrace of technological gewgaws. It's no big deal nowadays to have one actor onscreen in two different roles, but in 1989, when Fox appeared as Marty Sr, Mary Jr, and Marlene, it represented quite a coup du cinΓ©ma, and it shows its age not at all. CGI was just in its cradle then, and the very minor use of computer animation throughout the film is every bit as effective as its practical effects. The film's visuals haven't aged quite as well as its predecessors; but much better than some films half as old.

Still, though, the 2015 sequence - with all its details and its pop-culture meta-commentary and the like - is just a portion of the film - and not the only good portion, though it's probably the best. Though the film sags a bit in the middle (the alt-1985, basically), it picks up considerably once it hits the territory covered by Back to the Future. Zemeckis obviously poured himself into this movie, for the verve with which shots reflect images from the earlier movie, with which footage from the earlier movie is re-purposed and re-staged; just generally the ballsy degree to which events that seemed complete before are suddenly revealed to have new purpose and meaning; Back to the Future, Part II is one of the few sequels in history to force us to seriously re-consider the original film, without ever depriving the original of its basic integrity.

Most sequels aren't time-travel flicks; therefore most sequels don't get to recontextualise the original in such narratively fascinating ways. Taken as a pair, the first two Back to the Futures ask a number of unresolved and unresolvable questions about causality, order, and intention; and taken as a pair, they're also a hell of a lot of fun. That's what separates a top-drawer talent like Zemeckis from a routine hack: he can make an entertaining trifle meant to sell popcorn, and still infuse it with all kinds of structural inquiry that you can either pay attention to or not: and staggeringly, the film is equally enjoyable either way. Back to the Future, Part II is unique in the director's career in this respect - he is not given to structuralist or formalist experimentation - but that very loneliness is what makes the film such a loopy success. Not as exceptional and driven as the first movie, of course, but still a doozy of brain-bending comedy, dressed up in bright enough colors and broad enough silliness that even a child can have a real blast watching it. I should know, I was that child, three-quarters of a lifetime ago.

Reviews in this series
Back to the Future (Zemeckis, 1985)
Back to the Future, Part II (Zemeckis, 1989)
Back to the Future, Part III (Zemeckis, 1990)