Supernatural is now in its 15th and final season, and while we are sad to bid farewell to the Winchesters, there are still some places that the series could go. The main series, of course, will wrap up at the end of this season (and fans will just have to wait and see if Sam and Dean actually survive it), but there is always room for a spin-off or two! Admittedly, at this point, Supernatural has already attempted to launch two spin-offs via backdoor pilots; Bloodlines (about a hunter family in Chicago), and more recently, Wayward Sisters (about Jody Mills and her family of orphaned hunter-girls). Neither took off, but that doesn't mean that fans don't still want to see more.
The ideal scenario, of course, would be to see an existing character get to carry their own show - but there are some that would be perfect for their own series, and some that should really be left where they are. Just because a character is a fan-favorite, doesn't mean that they would be the perfect new lead...
Spin-Off: Charlie
If there's one character that every fan would agree they want to see more of, it's Charlie Bradbury. Charlie was originally a tech savvy civilian, but when she bumped into Sam and Dean on a case (and ended up helping them), she fell in love with the hunter life. Not only would it be amazing to see Charlie at her hunter-y best - rather than just popping up to help Sam and Dean - but she could also have a far more fantastical spin-off, based on the fact that she and Dorothy waged a war against evil in Oz. Yes, that Dorothy, and yes, that Oz. On top of all that, a Charlie spin-off would be led not just by a female character, but an LGBTQ character, which would be a welcome change. Supernatural may be an incredible show, but there's no denying that they have a bit of a problem with short-lived female characters.
No Spin-Off: Castiel
Castiel is another fan-favorite character, and it's easy to see why. He's an Angel, but he thinks for himself, he kicks ass, he messes up, and he has the best insults in this entire universe. However, Castiel doesn't deserve a spin-off because he's been the third-biggest character in the show almost since he first appeared in season 4. Fans have already seen him go from clueless angel through near-God, to rebel angel and honorary Winchester... there's just no natural place for this to go next. A Castiel prequel in Heaven would be surprisingly boring, as that was a time when the angels were all pretty much falling in time, and a post-Supernatural Castiel series would simply feel like a continuation.
Spin-Off: Bobby
The grumpy, brilliant, father-figure that is Bobby would be the perfect candidate for a spin-off... if it was set when he was a young man. Bobby hasn't always been the grumpy old man that he is in the show, of course. He was an energetic hunter alongside Rufus. He was a young man who fell in love and got married.
And of course, he was someone who took care of Sam and Dean at times - and who doesn't want to see tiny Winchester brothers making the occasional guest appearance in a new show? The only issue with a Bobby spin-off is that it might be a little too similar to the current series.
No Spin-Off: Adam Milligan
Adam definitely has the worst luck of any Winchester - and that's including Mary, who was murdered and torched on the ceiling above her baby's crib. At least she got to come back... and didn't have to spend any time being used as a chew toy by an angry archangel in Hell. The half-brother to Sam and Dean, Adam was only around for a short while before becoming Michael's vessel and getting locked in the cage. Sad for him, of course, but it doesn't leave much meat for a spin-off series, as he led an entirely normal life up until his appearance in the show.
Spin-Off: John & Mary
Back to the past again for this one - fans would love to see more of John and Mary Winchester when they were young. A surprising amount of their backstory has already been told, thanks to both flashbacks and time travel (and a few other handy devices), but there's plenty here to create their own show.
The romance between the two of them, the experience of growing up in a hunter family (that don't think they are the only one), a more extended look at that original demon deal... this would be a brilliant prequel. And, of course, this allows for fans to see both young Bobby and baby Sam and Dean, and everyone wants more of that.
No Spin-Off: Benny
Some fans might be rooting for a monster-centric spin-off, but if anyone wants to watch a show about vampires, there are already plenty out there to choose from. And while Benny, Dean's purgatory buddy, definitely does have some stories to tell, there may just not be enough to make it compelling for an entire show. A Benny-based episode? Absolutely. But a whole series? Not so much. That said, Benny did recently get a moment in the final season for fans to say goodbye... even if it was all a dream.
Spin-Off: The Men of Letters
There's just something fascinating about the idea of a Supernatural prequel (and it will be necessary, should the Winchesters fail to stop the final apocalypse this season!). This one, however, would be more of an ensemble series - and one with a clear end. Since season 8, Sam and Dean have known about the Men of Letters... an organization that dealt with hunters, monsters, lore, and all kinds of dangerous objects. Rather than focusing on the hunting side of things, a Men of Letters prequel could look at a more gentleman-spy angle, and focus on lore and history. This would also allow for the rest of the world to be brought in; there's already a British Men of Letters... are fans supposed to believe that they are the only other branch?
No Spin-Off: Chuck & Amara
Chuck and Amara are two of the biggest characters that really don't have a whole lot of backstory to them - and of course, they spent the past little while wandering the cosmos as gods. A Chuck/Amara roadtrip through the universe would actually make for a fascinating spin-off, but it might be going just a little too far from what fans expect. This kind of trippy, totally out-there show would be difficult to get right, which is an issue... and of course, without knowing how the story ends for Chuck vs the Winchesters, a spin-off might become pointless anyway!
Spin-Off: Gabriel
Gabriel, aka Loki, aka the Trickster - fans are still waiting for this guy to pop back up again before the finale. Sure, he's dead, but Gabriel is 'killed' all the time, and just keeps finding ways to come back (or to have tricked everyone into thinking that he was dead in the first place). Of all the supernatural beings on the show, and especially the angels, Gabriel and his wild ways undoubtedly make for some of the most interesting stories. And this wouldn't have to be a continuation, or a direct prequel. Watching Gabriel trick his way through any time period, or even just seeing what he was up to between Winchester sightings, would be a brilliant show for any fan.
No Spin-Off: Ash
Ash and the Roadhouse crew are definitely fan-favorites, and there may be space to see a Roadhouse sequel, where Ellen and Jo are able to act as the center for a whole ensemble of hunters. However, Ash solo just doesn't have what it takes to carry an entire show. This redneck hacker-hunter works best when he has other characters to play off, which is why he was so perfect at the Roadhouse. Plus, he specializes in hacking and getting so drunk he passes out on the pool table, neither of which really make for great viewing.