It's inevitable that successful televisions shows spark talks of spin-offs from either the creators or the networks. First there's a rumor, then an announcement, then excitement from fans. But with so many new and original TV shows conceived, proposed, and filmed each year, spin-offs have an uphill climb for approval from networks, no matter how popular the host show was. Most spin-offs never make it to the screen.

While there have been successful spin-offs like The Facts of Life and Frasier, there seems to have been an equal number of failed ones. Joey (from Friends) and The Lone Gunman (from The X-Files) are two spin-offs canceled in their second and first season respectively when the shows they were spun from were wildly successful.

Spin-offs typically take a character - usually a fan-favorite secondary character - or a plotline to expand into a separate series. Often, the original show would air a backdoor pilot - an episode introducing the idea of the new series - during a currently-running season to gauge viewership and interest. Based on response to the backdoor pilot, networks would approve or reject a spin-off.

This list of 16 TV Spinoffs That Never Happened showcases some that made it to the pilot phase and many that never even went past the idea phase. So as you read the entries, think to yourself - whether you are or were a fan of the show - if you'd watch the planned spin-off.

Bloodlines -  Supernatural

Supernatural Bloodlines

A spin-off to Supernatural began to become reality when mentioned at a panel at San Diego Comic Con 2013. It had a different title then (Supernatural: Tribes), but in 2014 was changed to Supernatural: Bloodlines. A backdoor pilot was filmed and aired as the twentieth episode in season nine of Supernatural.

The show was planned to take place in Chicago and would focus on monsters and hunters battling it out on the streets of the Windy City. Rather than focusing on any of Supernatural large cast of supporting characters, the spin-off would feature entirely new characters. After a lukewarm response to the backdoor pilot, he CW decided not to move forward with the show.

Currently, a spin-off called Wayward Sisters is being considered and has a backdoor pilot airing in the thirteenth season - this time featuring three beloved secondary characters from the main series.

 RipperBuffy the Vampire Slayer

Giles from Buffy the Vampire Slayer character poster

If you didn't watch Buffy the Vampire Slayer, you can still probably name either one or two characters or one or two actors from the show. Joss Whedon's iconic show ran for seven seasons and spans comics, board games, and books. One spin-off of Buffy that came to fruition was Angel, with David Boreanaz. Because there's so much material, there's even a "Buffyverse".

One of the popular characters from Buffy, Rupert Giles, was being considered for a spin-off on the BBC network. It would follow Giles in his younger years during his time in London. The show never proceeded past the idea stage since Whedon was giving quite a bit of time to Dollhouse and it was difficult to find actors and actresses appropriate for the BBC for the Ripper characters.

Ripper still manages to intrigue Buffy the Vampire Slayer's original creators and producers, but it's been recently said if Ripper does happen, it would most likely happen as a TV or feature film.

 How I Met Your Dad - How I Met Your Mother

How I Met Your Mother

When How I Met Your Mother ended, CBS was probably worried that the end of one of its biggest shows would drive people away, causing overall network ratings to sink. In 2013, CBS okayed a spin-off called How I Met Your Dad. However, the show would be about a brand-new character retelling her kids how she met their father.

The series would take place in the How I Met Your Mother universe, causing speculation the two shows would overlap or contain a crossover at some point.

A pilot episode was ordered, but CBS was less than impressed and eventually passed on the spin-off. Following that, CBS attempted to have people rework the pilot and storyline to make it better, but nothing worked for the network.

If you're a fan of How I Met Your Mother, there's still hope. Early in 2017, it was mentioned by Deadline that the spin-off is beginning again with a clean slate with new writers and the possibility the show will be on a different network.

 Rose Tyler: Earth Defence -  Doctor Who

Rose Tyler from Doctor Who looking off camera.

Billie Piper played Rose Tyler, a companion of Doctor Who in his ninth and tenth manifestations. When Rose left the tenth doctor at the end of the "Doomsday" episode, a spin-off series was proposed by producer Russell T. Davies that would be called Rose Tyler: Earth Defence.

The spin-off would most likely be about Rose Tyler on an alternate Earth that one of the Doctors called "Pete's World." She'd work at that alternate version's Torchwood Institute.

BBC was ready to go ahead with the spin-off, ordering episodes and creating a budget for the first series of the show. But in the final hour, Davies canceled the spin-off himself, stating Rose Tyler: Earth Defence was "a spin-off too far." It also lessens the importance of the Rose Tyler character if viewers saw her life continue outside of being a Doctor's companion.

12. Aquaman - Smallville

Aquaman struggles to breathe outside water in Smallville

In the fifth season of Smallville, an episode called "Aqua" aired that accidentally became a backdoor pilot for a proposed spin-off series with Aquaman. That episode was one of the highest-rated episodes of the series and the creators saw the potential for Aquaman to have his own series.

However, the creators didn't consider Aquaman to be a spin-off series in the traditional sense, mainly because the actor who played Aquaman in the "Aqua" episode wasn't going to reprise the role and the spin-off would be a new version of the Aquaman legend.

A pilot was filmed, but the CW passed on greenlighting a series, giving no real reason why they did so. You can still watch the pilot episode on iTunes and other digital stores and in some Smallville DVD and Blu-ray sets.

 Girlfriends - Friends

Arguably one of the best sitcoms of all times, Friends was about six young men and women as they lived in Manhattan and handled relationships, work, and life in general. The series spawned a failed spin-off, Joey, which took Joey Tribbiani to L.A. to pursue his acting career in a more hardcore capacity. Joey was canceled after two seasons.

While the creators weren't keen on NBC's need for the Joey spin-off, they were interested in a series with Phoebe Buffay, who'd live with Charlie, played by Aisha Tyler. The show was called Girlfriends in the initial stages, but creators David Crane and Marta Kauffman never got the show past the idea phase.

Given the obvious talent - and present day success - of its leading ladies, it's possible that the Phoebe spin-off would have been successful, unlike Joey.

 Marvel's Most Wanted - Agents of Shield

In an episode of Agents of SHIELD, the characters Bobbi Morse and Lance Hunter (Adrianne Palicki and Nick Blood) left the group to go out on their own, giving the impression they wouldn't return. This was setting up a spin-off called Marvel's Most Wanted where Morse and Hunter decide to go into hiding from all the enemies that want to cash in on the bounty that was on their heads.

For the second time, ABC passed on the spin-off, despite starting the development process for Marvel's Most Wanted during previous season's Agents of SHIELD. But when new shows were announced for 2016 - and Agent Carter was canceled - the spin-off was not on the list for the new season.

With the popularity and success of Marvel shows on Netflix, it's possible Marvel's Most Wanted could find a home with the streaming service.

 Assignment: Earth - Star Trek

The Star Trek universe has endured for over 50 years, with multiple TV series and movies - including the upcoming Star Trek: Discovery television series - but in 1967, Gene Roddenberry began plotting and scripting a new show called Assignment: Earth, which had been meant as a new series, with nothing to do with Star Trek.

Roddenberry's pitch failed, so he adapted his ideas in to a Star Trek episode, which aired as the season two finale. Like many spin-offs, the episode "Assignment: Earth" was planned to introduce the new series, but was unsuccessful in convincing the network, critics, and viewers that Gary Seven and his crew should continue on its own. The following year, Star Trek was canceled.

The concept lives on with IDW comics: you can read about Gary Seven, his secretary Roberta, and his shape-shifting cat in Star Trek: Assignment: Earth comics.

 The Farm - The Office

Dwight hugs family on his farm on The Office

During the ninth season of The Office, NBC aired an episode titled "The Farm". It focused on Dwight's Aunt Shirley passing away and leaving her farm to Dwight and his siblings. One caveat, though: they must live together on the farm, otherwise she wouldn't leave it to them.

"The Farm" aired as the seventeenth episode in the season - essentially six episodes from the series finale - and had been planned as a backdoor pilot to the spin-off of the same name. But instead of sticking with Dwight and his siblings' storyline, the creators added a second, unneeded storyline with Todd Packer seeking revenge on those in the office because he was fired. These two plots, which were unrelated to each other, may have caused confusion on what the creators' vision actually was for The Farm.

The episode rated low overall - with viewers and critics - and NBC ultimately decided against picking up the spin-off.

Jackie Chiles Spin-off - Seinfeld

Jackie Chiles in Seinfeld

Seinfeld was a show you either loved or hated. This "show about nothing" has garnered numerous awards and ranks high on "Best of" lists about televisions shows. Through its nine seasons, Seinfeld introduced many memorable characters like the Soup Nazi, the Close Talker, and Peterman.

Kramer often partnered up with one character when he wanted to sue a company or person and needed representation - the fast-talking lawyer Jackie Chiles. The courtroom antics of Jackie and Kramer are some of the most hilarious on the show, as Chiles's big vocabulary and thought process often backfired on him and Kramer.

After Seinfeld ended, the actor who portrayed Jackie Chiles was interested in creating a spin-off of the character. Nothing came from the idea, but Phil Morris filmed a few skits of the character for the comedy website, Funny or Die.

 Tales from Springfield & Krusty - The Simpsons

A promotional picture of Krusty the Clown

The Simpsons series was a spin-off from The Tracey Ullman Show. The cartoon started as animated shorts filling in as segues or transition pieces. Fox greenlit The Simpsons as a half-hour sitcom, and since 1989, it has run over 600 episodes. Currently, the show is renewed through 2019.

Many spin-off ideas were generated over the years as The Simpson became a television phenomenon. Most ideas were short-lived, but two in general almost made it to air. The first was called Tales from Springfield, where the focus would be more about other people than the Simpson family, most likely a background character. The idea was promising, but there wasn't enough staff to concentrate on two animated shows.

The second spin-off was a live action Krusty the Clown series simply titled Krusty. Krusty would move to L.A. and get his own talk show. A pilot script was even written, but negotiations over the show faltered and never went past that point. Creator Matt Groening then cancelled the project.

 More Roseanne - Roseanne

Roseanne original cast promotional image

Roseanne lasted nine years, a tremendous feat in any decade of television. The show epitomized the plight of the working-class family, which is why it was a hit for ABC.

In the spin-off, the attention would continue to be on Roseanne, but this time in a new setting and situation. She'd still retain her married name Conner. If you remember the series finale, it left open any number of story possibilities for additional spin-offs or seasons.

The network for the original Roseanne, ABC, decided not to go forward with the spin-off. Roseanne's production company wanted more money than ABC wanted to spend on the new show. Roseanne Barr went to other networks, but no one went with the spin-off.

Currently, instead of a spin-off, Roseanne is set to be revived with an eight-episode limited run taking place fourteen years after the first series.

 Eric's POV - Undeclared

The cast of Undeclared in Undeclared

Judd Apatow followed up Freaks and Geeks - canceled for a shocking reason - with Undeclared, another show of his that created a cult following. However, Undeclared was canceled after one season. It was then that Apatow turned to film and released hilarious hits like The 40-year Old Virgin, Knocked Up, and Funny People.

The Undeclared episode "Eric's POV" was filmed as a backdoor pilot to introduce a spin-off of the same name, featuring future HIMYM star Jason Segel. The strange part about this episode making it to air was that Undeclared had already been canceled at that point. Apatow had also said if the show went to a second season, another episode would have come from "Eric's POV", detailing more events from the birthday party in that episode.

"Eric's POV" ended up airing as the series finale, and no more was mentioned about furthering the show or the spin-off.

Audrey Horne Spin-off - Twin Peaks

Twin Peaks's Audrey Horne

David Lynch's Twin Peaks created a cult following in its short run. With a quirky cast of characters to rival a Stephen King novel, Twin Peaks had many storylines running at once that all related to each other in amazing ways. Recently, a Twin Peaks limited-run revival called The Return ended after eighteen episodes.

One particular character was a fan favorite. Audrey Horne, played by Sherilyn Fenn, found a way to cause trouble for other characters - especially her father - with finesse and calculation. In the first season, she becomes infatuated with Agent Cooper (Kyle MacLachlan) and assists him in his investigation into the death of Laura Palmer.

During Twin Peaks, David Lynch had planned a spin-off series for Audrey Horne where she'd move to Hollywood. But the concept didn't move forward. However, his idea for the spin-off turned into his successful movie, Mulholland Drive.

 Mona - Who's the Boss?

Most remember the 80's sitcom Who's the Boss?, starring Tony Danza and Judith Light, and how their characters followed a "will they or won't they" path of love through the series. And most remember Katherine Helmond's character Mona, who was Angela Bower' sexy and sarcastic mother.

After the first proposed spin-off from Who's the Boss? failed, producers envisioned a second spin-off called Mona, where Mona would visit her brother Cornelius in Manhattan. He had purchased a run-down hotel, and, seeing how much help he needed to run it, Mona decided to stay and assist him. This was showcased in a two-part episode during the third season of Who's the Boss?

But the network didn't go forward with the spin-off, citing their fears of losing viewers if Mona left Who's the Boss? for good. They had the writers redo the ending where Mona returned to the garage at Angela's home to live.

 Kick it With the Flygirls - In Living Color

In the early 1990s, Keenan and Damon Wayans created, produced, and wrote a sketch comedy show called In Living Color. The show launched careers of future big stars Jim Carrey, David Alan Grier, and Jamie Foxx. The variety show also had live musical performances and dancers who were called the Flygirls. Some recognizable names that emerged from the dance troupe were Carrie Ann Inaba, Jennifer Lopez, and Rosie Perez (a choreographer).

In 1991, one year after the show first aired, Fox announced the Flygirls would have their own hour-long show called Kick it With the Flygirls, which would feature hip-hop artists, rappers, and other acts. Shawn Wayans would be the host.

It seemed the show was going to proceed - Fox held auditions for additional dancers in L.A. and New York, but Kick it With the Flygirls went no further than that.

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Was there a canceled spinoff that you would have loved to see? Or is there a current show that could easily spawn a successful spin-off? Let us know in the comments!