Sci-fi tv shows that went on too long include Lost, Supernatural, and ALF.
Some of the best sci-fi shows never had a full first season, notably Firefly, but other shows seemed to be on the air forever. Some were to reach the bar for syndication, or an attempt to keep a hot series going after a star left, but for most of these, it’s not as obvious. Often, sci-fi tv shows collapse from doing too much, pushing the story to more absurd lengths, and losing the audience in the process.
This list is a mix of everything that goes wrong when shows go beyond the natural narrative endpoint.
10. The Flash – 9 Seasons
Fans of The Flash have a good case for arguing that the long-running Arrowverse series became The Virtue for its final season, as Grant Gustin’s speedster was routinely sidelined for his supporting cast. What started out as a focused narrative around the fallout of an accident at STAR Labs quickly spiraled into a dimension-hopping tale, often with actors playing multiple versions of themselves.
As time went on, more fans left the series that, as with most of the sci-fi shows on this list, collapsed under its own weight. If the show had ended earlier, around the Crisis on Infinite Earths cross-over, it would have spared fans the ultimately pointless trips to the future, The Virtue, and one of the worst finals seasons since Game of Thrones.
9. Sliders – 5 Seasons
Sliders is an underrated sci-fi tv show from the mid-90s all about “sliding” between dimensions, and a young Jerry O’Connell led the cast. As the years went on, the dimension-hopping concept got muddied, and cast members were replaced as their characters died in shockingly horrifying ways.
That included the loss of O’Connell, only to be replaced by his brother Charlie O’Connell as an alternate-reality Quinn, and then a third Quinn was introduced for the final season, played by Robert Floyd. Sliders should have ended with Season 3 when the show left Fox and became focused on a storyline about dimension-conquering aliens.
8. Smallville – 10 Seasons
Smallville was a victim of its own success, and while the final season still had some of the best episodes, including the first appearance of a live-action Booster Gold, but then fans were dying for Tom Welling‘s Clark Kent to put on the tights and take to the air. The rule of “no tights, no flights” that governed the series became an albatross, forcing the world to develop without an actual Superman.
If Smallville ended years earlier to be replaced by a new series, Metropolis, it would have done the story justice. The rare sci-fi tv show that was a joy to watch from beginning to end despite the ups and downs, it still could have been better and remains the best version of Superman on the small screen.
7. Charmed – 8 Seasons
No, Charmed should not have ended when Shannon Doherty left the series, but it should have stopped with the Season 7 finale, “Something Wicca This Way Goes,” which would have been a satisfying end to the tale of the Halliwell sisters. Instead, Season 8 introduced Kaley Cuoco as Billie, a character intended to headline a future spin-off that stole the spotlight from the three leads in episode after episode.
Charmed made history at the time as the longest-running female-led series, a distinction it still holds among sci-fi and fantasy shows, yet it’s clear that everyone involved intended the show to end with Season 7.
6. The X-Files – 9 Seasons
One of the greatest sci-fi tv shows of all time, The X-Files, should have ended with Season 7 when David Duchovny wanted to leave, or at least Season 8 after a full season of Robert Patrick filling in as Agent Doggett. Gillian Anderson stuck around for the remainder of the show, two full seasons, but the magic between the original leads could never be replicated.
On another note, the over-arching conspiracy could have been solved earlier, with the series finale somehow having almost nothing to do with aliens. Later shows would also suffer from going far too long without providing answers, showing that they learned nothing from when the best of the genre managed to drop the ball.
5. ALF – 4 Seasons
ALF only went for four seasons, but try and read the amazing oral history put together by Mental Floss without feeling bad for the cast of the show. The series about a cat-eating alien was shot on an elevated stage littered with trap doors, and the puppetry was so demanding that it took 20 hours to shoot a 22-minute episode.
The immensely popular sci-fi tv show made it to 102 episodes over four seasons, enough to make it to syndication, which at the time, was where the real money was for a television series. The herculean task of stretching the wafer-thin plot far enough for syndication may not have been worth everyone’s sanity.
4. The Vampire Diaries – 8 Seasons
The Vampire Diaries only lasted eight seasons, but it spawned a successful spin-off, The Originals, which then had its own spin-off, Legacies. Yet The CW vampire drama was already running on fumes when the first immortal, Silas, was revealed to be a doppelganger for Stefan (Paul Wesley). When actors start pulling double-duty, it’s usually a sign the end is near, though, to the show’s credit, Elena and Katrina were doubles played very well by Nina Dobrev for most of the show’s run.
Once again, the problem facing The Vampire Diaries was seasons of over 20 episodes, requiring characters to become friends, enemies, and lovers along an endless carousel. Plots and pairings were burnt through at record speed, putting the show in danger long before Nina Dobrev left after Season 6.
3. Supernatural – 15 Seasons
Supernatural went for 10 seasons too long, with the fandom largely agreeing that Season 5 was the best endpoint. Yet the adventures of the Winchesters, Dean (Jensen Ackles) and Sam (Jared Padalecki), continued for another decade, forcing poor Misha Collins to wear a trenchcoat for 12 years straight.
The battle between the Winchesters and Lucifer (played by the underrated Mark Pellegrino) should have been the ending, and “Swan Song,” the Season 5 finale, remains the series’ highest-rated episode. Again, a sci-fi tv show started messing around with alternate dimensions, including an Apocalypse World, and back-door pilots, in this case, the potential Wayward Sisters series that never happened.
2. Lost – 6 Seasons
Where to start with Lost, the show that influenced countless other sci-fi tv shows but managed to be the poster child for shows that never bother explaining what’s happening? Decades after the series finale, fans are still debating what the show was even about in the first place.
The list of unanswered questions (What’s the Light?) is massive, and another one of satisfying answers is significantly shorter (Why are some of them ageless?), but the collection of unsatisfying answers (the Smoke Monster) is even longer. Lost would have been better served with shorter seasons and a tighter plot that ideally wrapped up around Season 3, which seems to be the perfect length for a mythology-heavy sci-fi tv show.
1. The Walking Dead – 11 Seasons
If it wasn’t for Jeffrey Dean Morgan’s electric portrayal of Negan, The Walking Dead would have been better off ending with Season 5, either showing the fall of Alexandria or ending on a slightly more hopeful note. After dealing with The Governor and the residents of Terminus, the narrative was left to spin its wheels for another seven years, repeating the same cycle over and over again.
Yet The Walking Dead was a ratings hit; even with falling ratings each year, it was incredibly popular and set records on a weekly basis at one point. A sci-fi tv show that peaked early, the series has already had a few successful spin-offs, but now multiple sequel series are starting to pop up.
There’s no more blood to get from the zombie corpse of The Walking Dead, and it would be remembered fondly if it had been canceled earlier.