Supernatural's 15th and final season in 2020 marks the end of a television institution. The series was one of the properties that newborn network The CW inherited from The WB's closure in 2006, along with Gilmore Girls and Smallville, both of which Jensen Ackles and Jared Padalecki had previously starred on. Supernatural has outlasted of The CW's inaugural lineup of scripted dramas, even those that began their runs years later. There's certainly an "end of an era" feeling surrounding its departure.

But nostalgia alone isn't enough to keep a genre series going for longer than any other in the history of American broadcast television. An equally long-running joke among journalists and TV fans alike is that, when the apocalypse comes, only cockroaches and Supernatural will be left. (Oh, and Cher, of course.) The crux of the joke rests on the disbelief that, after over a decade on the air, Sam and Dean Winchester and their trademark Impala aren't running on empty by now.

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Sure, 14 seasons means that story beats are recycled and the stakes are harder to raise, but ask any Supernatural fan why the show has gone on as long as it has and they’ll tell you it’s simple: Ackles and Padalecki have lost none of their chisel. And then they'll tell you, with more seriousness, that it's because -- aside from a post-Season 5 rough patch -- the show has just never gone stale.

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It’s a biased opinion, of course, but one supported by a positive critical consensus on Rotten Tomatoes of 88 percent, with a 90-percent approval rating from audiences. According to iMDB’s user review aggregation, episodes consistently score between eight and ten. The lowest scoring episode is Season 1's "Bugs" with a 7.1, and the second highest -- right behind the Season 5 finale that was originally intended to end the show -- is Season 14's "Lebanon" with a 9.6. Not exactly the track record of a show way past its prime. As a whole the show has an 8.5 which, for context, is only just behind critical darling Game of Thrones' 9.5 and slightly ahead of the wildly popular The Walking Dead's 8.3.

Despite this strong track record, Supernatural still gets lumped into the Shows You Won’t Believe Are Still On The Air category, its record-breaking success considered a misnomer or, at best, a fluke; lightning in a bottle. Quality in art is, of course, highly subjective. There are those that feel the show's continuation after it's planned ending has been pointless, while others have never found the Winchesters' adventures their cup of diner coffee to begin with. The latter speaks to the double-edged sword of genre storytelling: Satisfying a particular niche for some means turning others off.

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But, one of Supernatural's most successful facets isn't just its genre adherence, but also its genre bending. It's part American Gothic, part the Great American Road Trip. It has one foot firmly planted in horror cinema while the other is in the world of slapstick comedy. Suitably, episodes range from heavy discussions about the morality of killing and the impact a life of violence has on a person's psyche, to Sam and Dean being zapped into an episode of Scooby-Doo. The brothers have done the expected, like battling demons, angels, vampires and ghosts. But they've also done the unexpected, like punching Hitler in the face, discovering the land of Oz, watching a musical about themselves put on by Destiel shippers and even meeting the actors who play them.

NEXT PAGE: Supernatural's Main Characters Are Effortlessly Likeable

Supernatural/Scooby-Doo crossover

You'd think plotlines like these would strain the show beyond credibility for fans, but, through all of this ridiculousness, Supernatural remains anchored by its characters. Sam and Dean are effortlessly likable in their ordinariness. Their work is grueling, life-risking, emotionally scarring and completely thankless. They aren’t famous and adored like your average superheroes. Their jobs are, like a lot of ordinary folk who do important, routine things for the well-being of others, unseen and unrewarded. A typical episode of Supernatural ends without fanfare and mass applause from the rescued masses, but with Sam and Dean drinking a beer on the hood of the Impala as if they've just clocked off.

Sometimes there are hugs and tears, too; a level of consistent emotional vulnerability that has ensured that the male-driven show has managed to steer clear of the shallow chauvinism and bravado it could so easily have slipped into. God and Death aside, Sam and Dean’s profound bond is the glue that binds the Supernatural universe together and pushes the narrative forward. Viewers invested in them and their relationship will travel with them wherever they go.

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Beyond all this, however, just how does a show that can’t rely on the episodic storytelling crutch that comedies and procedural dramas do keep its audience coming back over the span of more than 300 episodes? Particularly, one that can’t compete with the likes of Game of Thrones and The Walking Dead for ratings.

In some ways, Supernatural's moderate viewership is actually highly beneficial. Because a consistently high critical and audience reception doesn't ensure immortality in the entertainment industry. Like Sam and Dean, Supernatural owes its ripe old age to one thing -- family. The #SPNFamily, which is the cast, crew and, crucially, the fans. Cultural phenomenons like Game of Thrones instead have a fan "community" because they're too horrendously large to form the kind of intimate bond that the devotees of cult series like Supernatural can. 

Supernatural is still the most blogged about TV series on Tumblr, the most written about on FanFiction.net and has conventions around the world dedicated to it in almost every month of the year. Attendees can expect frequent appearances from the cast and crew (and the odd Bon Jovi jam sessions.) The fanbase even has its own representation in the show through the in-universe fans of the Supernatural novel series penned by the prophet Chuck, as well as the aforementioned Supernatural musical adapted from those books. There have even been shout-outs to the popular Wincest ship. Supernatural doesn't just wink and nod at its audience, it makes them part of the fabric of the show.

Tuning in to a lot of big, fantasy epics these days is like playing survival bingo. Tuning into Supernatural is like checking in on old friends. The scares and surprises may have dulled over the years, but there's a lot to be said for quality comfort TV.