The cliffhanger is one of the most useful tricks in the book for TV writers: Not only does it keep viewers coming back week after week to find out whether our favorite heroes will finally meet their doom (spoilers: they won't), but it also discourages network executives from pulling the plug on a show before the story is resolved. That's why huge, dramatic cliffhangers are so popular in season finales -- if the execs cancel the show before we find out what happens next, they'll look like giant douchebags.
However, if your show isn't doing all that well in the ratings, that sure as hell won't stop said execs from giving it the ax. So let's take a moment to sympathize with the cult followings of these shows who will never know how their stories turned out ...
6 Terminator: The Sarah Connor Chronicles -- John Kills the Whole Franchise
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The Sarah Connor Chronicles was a TV spinoff of the Terminator movies that took place after the events of T2 : A teenage John Connor and his mother, Sarah, having prevented the future annihilation of mankind at the hands of killer robots (but not really), are transported from the '90s to our present ... because look, they could either spend the show's budget on grunge shirts and Spice Girls posters, or they could use it on killbots and explosions.
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Guess which one they went with.
Anyway, the show mostly dealt with several time travelers from the machine-dominated future bumping into each other: Terminators sent to terminate things, members of the future resistance sent to terminate Terminators ... hell, they even had Terminators sent to terminate Terminators. In short, it was a fun time for the whole family.
Basically, they undid the whole Terminator franchise in two minutes.
In the last episode, a time machine dumps young John Connor and Weaver the Friendly Terminator in the post-apocalyptic future where John is the legendary leader of the rebellion against the machines. However, because John left his spot in the present and never grew up to resemble Christian Bale, no one in this future has heard of him ... effectively wiping out the premise for the entire series. Even John's dad, Kyle Reese, is there and doesn't recognize him, and that guy was like the Connor family's #1 fan.
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And without future John as his role model, Kyle ended up going with a decidedly more metrosexual look.
Then a confused John sorta stares at everyone for a really long time and the credits roll. What happens next? How will John go back to the present and fix the timeline? We'll never know, because the show was cancelled after only 31 episodes. One of the reasons given was that it was too expensive, so maybe they should have gone with the grunge shirts instead of the explosions after all.
So, to recap, as of now future John Connor doesn't exist and Skynet has no reason to send Arnold Schwarzenegger back to the first Terminator movie to kill John's mother, erasing the entire series from existence, along with several million dollars from James Cameron's bank account (we're guessing he eventually went back to trucking in this reality). But hey, at least this means T3 and Terminator Salvation never happened.
5 Twin Peaks -- Agent Cooper Gets Possessed, Then It Ends
Twin Peaks was ostensibly a show about FBI agent Dale Cooper's investigation of the murder of teenager Laura Palmer, but in practice it was about literally everything else, from backward-speaking dream dwarfs to aliens to that fine, fine coffee. In fact, the Laura Palmer mystery was wrapped up halfway through Season 2, although the party responsible, an incorporeal demon called Killer Bob, was still out there.
Lurking behind your furniture.
Everyone's favorite character becomes possessed by a demonic rapist.
In the Season 2 finale, Agent Cooper goes into a mysterious extra-dimensional place called the Black Lodge to rescue his love interest, but instead he bumps into an evil version of himself. Rather than settling for that and finding out what it's like to give yourself a BJ, Cooper confronts his doppelganger and only one of them comes out of the Lodge -- the evil one. In the last scene, Bad Cooper smashes his head on a bathroom mirror and we see that his reflection is that of Killer Bob, the demon who raped and killed Laura Palmer.
It's that or Hobo-Gandalf.
And that's how the show that had captivated America one year earlier ended -- not with a delicious cherry pie, but with blood running down a defeated Cooper's smiling face. In an attempt to save Twin Peaks from cancellation, the producers had brought back series creator David Lynch for this episode, and while he provided the David Lynchest 50 minutes imaginable, the ratings apparently still sucked. This means that Killer Bob has been joyriding in Agent Cooper's body for 20 years now -- even if Coop did escape the Black Lodge at some point, he'd have serious brain damage from all those intentional bumps on the head.
To add insult to injury, Lynch went on to make a Twin Peaks movie ... but it was a prequel, for the most part, so it didn't continue the cliffhanger. Of course, knowing Lynch, if he did try to provide a resolution, it'd be something like "Bad Cooper eats a squirrel and transforms into Michael Jordan, the end."