Has there ever been a series of films with the same characters but with switching genres? Like having an action film like Die Hard, where John and Holly McClane get back together at the end, followed by a sequel that is a romantic comedy about their relationship, followed by science fiction that is about their son getting abducted by aliens. I can't think of any real examples, but I think in 100 years of film something like that must have been attempted at some point, must it not?
The Evil Dead series. The first installment was a straight up horror movie. The second was a horror comedy. Third was a fantasy comedy.
Arguably, the "Alien" series. Alien was a horror story with the trappings of science fiction, while Aliens was more a war movie in a science fiction setting. Alien 3, of course, was just crap.
Terminator. Of course, you have to ignore the last two films for this to work, but everyone already does that anyway. Terminator 1 was a horror movie Terminator 2 was an action flick Evil Dead. Evil Dead 1 was a straight up horror film Evil Dead 2 was a horror/comedy Army of Darkness was a swords & sorcery film
Highlander should qualify. And this may be an off-the-wall example, but technically Abbott and Costello Meet Frankenstein meets the definition. It's part of a "series" in the sense that it's a follow-up movie to the Universal monster movies. It has the same characters (and several original actors). And it's in the comedy genre instead of horror.
The Fast and the Furious franchise has moved from street-racing to straight up heist films. But the best example off the top of my head is the Rambo V plot that was floated around for a year or two that would have taken the franchise into science fiction territory.
I tend to see Pitch Black and The Chronicles of Riddick as an example. The former is a fairly grounded science fiction thriller -- it has a few scientific implausibilities, like the two-ringed planet and the inconsistencies of the moon's orbit, but compared to most SF movies, it's quite plausible and bordering on hard SF. Yet the sequel is this way-out space fantasy, and it takes this guy who was just a human criminal in the first film and reinvents him as the Chosen One of some alien race. Also there's the Marvel Cinematic Universe -- we've seen Captain America go from starring in a WWII film to starring in a modern sci-fi action film. How about the Inspector Clouseau franchise? The first few films were crime/detective comedies, but then The Pink Panther Strikes Again took an abrupt turn into sci-fi with a madman holding the world hostage with a disintegrator-ray doomsday weapon. The Dick Tracy comic strip also made a shift from crime stories to sci-fi in the '60s, though it reverted again some years later. Batman comics went through a similar change in the '50s and '60s. I'm pretty sure I've heard of a comic-strip hero from the '30s or '40s who started out as a flying ace or something and was then reworked into a space hero in the Flash Gordon vein, but I can't remember what it was. And the first couple of issues of The Fantastic Four were basically monster comics, with the shift toward superhero-vs.-supervillain stories happening around issue 3 or 4. Oh, how about the Lou Grant character being spun off from the half-hour sitcom The Mary Tyler Moore Show to the hourlong drama Lou Grant?
The Fast franchise - from undercover cop story to heist flick in Five. I really wish we'd gotten a The Mummy ('99) sequel like that.
Now that you mention it, Jason X did the same thing. And the Basil Rathbone Sherlock Holmes series jumped both time periods (Victorian London to WWII London) and genres (crime/mystery to WWII/spy).
The Godzilla series has gone through everything from straight-up horror (the original, arguably "Godzilla vs. the Smog Monster" and maybe even "Godzilla vs. Destroyah"), comic book style action adventure involving alien invasions ("Invasion of the Astro Monster" and "Destroy All Monsters"), fantasy (any of the films involving Mothra, particularly those bearing her name) James Bond esque spy intrigue ("Ghidorah, the Three Headed Monster"), and even the bare elements of a heist film (as seen in "Ebirah, Horror of the Deep" and "Godzilla vs. Biollante"). "Godzilla vs. Space Godzilla" even flirts with being something akin to a teen romance at times, much to the horror of the fanbase at large.
Kill Bill. While they are both action movies, the second one builds up the plot a lot more and has a very different feel to it. Not that I don't like it, they're both good movies. But they have very different feels.
Universal Soldier: Day of Reckoning deviated greatly from what the prior movies have been like. I never saw it, but supposedly it's more of a psychological thriller... with excessive violence even for a Universal Soldier movie.
They are completely different though, the first plays as a kung fu film, the second as a western (and for the record I really like the first and really don't like the second!)
Sure, but my point is that I'm not sure you can really call something a "sequel" if it's just the second half of a single 2-volume story.