With fifteen seasons and three hundred and twenty episodes, all at forty-plus minutes, Supernatural is not only one of the most beloved shows by its fandom but also one of the most expansive out there. There are many characters, both minor and major, introduced in the show and a tonne of narrative threads that could easily be pulled into a series.
A Supernatural spin-off has been talked about for years, and with the show over and Sam and Dean's characters laid to rest, now would be the time for one, if ever. There have been many rumors for specific shows over the past decade, and the fandom, in its passionate, obsessed state, has its own ideas for spin-off shows away from the Winchester brothers.
"Wayward Sisters"
The "Wayward Sisters" show has been a well-documented saga over the years, with the show very much on the table as a spin-off for the beloved series but never picked up by the CW.
Nevertheless, this can easily be a never-say-never scenario. Many fans want to see a show revolving around the beloved Jody Mills and Donna Hanscum and their family of fierce women. There is a lot of potential for the show, especially in a world without Sam and Dean to protect it.
Alternate Worlds/What If?
Speaking of different worlds, that was one of the more out-there concepts Supernatural presented in its later seasons, and also, thankfully, one of the most interesting, even if not all the characters presented worked well.
A show looking into these alternate universes with and without the Winchesters would be great. That would be very similar to the 'What If?' show idea that every single fandom in the world dreams of for their franchise, especially since Marvel announced it would be delving into that project for the MCU.
John Winchester (& His Journal)
Before Sam and Dean were out there on their own, stopping the Apocolypse, defeating God, and dying on rusty nails, their father, John Winchester, was out hunting anything and everything on route to the demon who killed his wife.
On this journey, John crafted one of the most important things in Sam and Dean's lives and careers, his journal. A show revolving around John's hunting, without the boys, when they were kids, as he creates an encyclopedia-esque hunting guide, would be nothing short of fantastic and would only improve John's character and story.
Samuel Colt
One of the most significant aspects of John's hunting down of Azazel was retrieving the mysterious 'Colt,' a gun that could kill almost anything, including demons, with its bullets, a gun created by famous hunter Samuel Colt.
Many fans have speculated about the value of a Samuel Colt show. He was a phenomenal hunter; he managed to create this incredible weapon somehow, and not too much else is known about him. Colt appears in "Frontierland," but a short show taking place before then detailing his life as a hunter and the creation of the Colt could add so much weight to the gun's story in the early seasons of Supernatural.
The Men Of Letters
The Men of Letters are a fascinating bunch, especially due to their differences to Sam and Dean and their British chapter, who fans pretty universally despise. But, on top of that, they have such an expansive history that has yet to be properly explored.
A show about the group has so many possibilities. From the accumulation of the lore in the Bunker to their encounters and relationships with hunters, the show could answer many fans' questions and be a good time on top of that.
Roadhouse Ensemble
One of the longest-running fan dreams/theories of a potential spin-off to Supernatural has been a hunter ensemble. The common consensus is that the Roadhouse is the perfect setting for such a show.
Seeing Ash, Ellen, and Jo in action alongside the slew of hunters who come in and out of their bar on the daily has a lot of potential. While the ten seasons post-Roadhouse family added a plethora of potential spin-off ideas to the minds of fandoms, this one remains, and it would be one of the best options for some sort of monster-of-the-week show akin to Supernatural's early seasons.
Young Bobby & Rufus' Hunts
Along those same lines is a potential Bobby and Rufus show, which so many fans have clamored for ever since the pair of characters were introduced early in the show and were shown to have not only chemistry but also history as partners.
Seeing younger versions of these fan-favorite characters hunting without the likes of Sam and Dean around, showing more explicitly the history and tension between them, and just seeing them banter with each other would make for a great series, and arguably a better monster-of-the-week show than a Roadhouse version.
Rowena, Queen Of Hell
Moving away from the potential prequel stories and onto a sequel, one of the show's most popular characters is Rowena MacLeod, a famous witch, mother of Crowley, and, by the end of the show, Queen of Hell.
As soon as she was revealed to be in the position her son once held, fans immediately speculated about a potential spin-off. The idea of Rowena as Queen of Hell is not only fresh in fan's minds but has so much potential given her attitude, her powers, and the fact that many people have sought the throne of Hell before, and it has only been seen held by demons, not witches.
Crowley, King Of Hell
Speaking of Rowena's son, the King of Hell, Crowley is another of the show's most adored characters with a phenomenal arc throughout his time on the show, which so many feel was cut too short, especially considering he never appeared again.
Crowley's past before the Winchester's is fascinating, and for years fans have speculated about Crowley's rise from a nobody in Scotland to the King of the Crossroads to the King of Hell itself. A series detailing this rise with all the sass of Crowley and less of the Winchester drama would be welcomed with open arms by fans.
The Angels, Heaven, & Hell
One aspect of Supernatural that was never explored to the point where it lived up to its narrative potential was the history of Heaven, Hell, and the Angels; both ironic and annoying considering how repetitive the Angel's stories got in the tail end of the show.
How it would work and when exactly it would take place is unknown, of course. But, much of the fandom has wanted to see how it all came to be, how Chuck created it, how the Angel's survived and thrived without him, how Heaven and Hell truly split. There is a lot of potential for mind-blowing programming for Supernatural fans related to the Angels.