When The WB debuted a low-budget comedy about a teen girl vampire slayer in the spring of 1997, no one expected it to make much of an impression — let alone become a bona fide pop culture force. But since the launch of Buffy the Vampire Slayer 20 years ago, TV has never been quite the same.

So when TV critic Emily Nussbaum declared, in 2014, that 1999 had marked a turning point for television, it wasn’t just because 1999 was the year The Sopranos debuted. It was also because 1999 was when Buffy, starring plucky ’90s darling Sarah Michelle Gellar, was at the height of its powers during its excellent third season.

Wrote Nussbaum at the New Yorker:

[1999] was a year when I was not yet a professional TV critic, just a woman, standing in front of a television show, begging everyone to love it. Every week, I watched The Sopranos and Buffy the Vampire Slayer; I was an avid fan of both, convinced that [Sopranos creator] David Chase and [Buffy creator] Joss Whedon were turning television into something radical and groundbreaking, the former by deconstructing the mob genre (as well as capitalism and psychotherapy), the latter by forging a mythic, feminist-inflected meld of horror, comedy, and teen drama.

You could go further, we would argue. You could say that essentially all of TV drama in 2017 is thanks to one of those two shows. The Sopranos and Buffy didn’t just change television. They blew up established formats and made the people who made TV rethink how they approached the medium.

But even now — two decades later, long after the show established itself as a TV classic — Buffy has yet to entirely get its due. Yeah, the show’s title is a little goofy, and its cheesy effects haven’t aged particularly well, and it’s based on a truly regrettable movie, and some of Whedon’s pop culture references have been lost to the mists of time. But Buffy is a genuine TV watershed, a landmark that deserves serious attention.

For as much as The Sopranos changed how TV is made, Buffy changed how its stories are told, and its influence is everywhere. Showrunners across the spectrum of the medium — from Shonda Rhimes to The Vampire Diaries’ Julie Plec to Supernatural’s Eric Kripke — have talked about how it influenced them. And those are just three names pulled essentially at random. Listing every showrunner who’s named Buffy as an influence would quadruple the length of this piece.

So, in honor of the series’ 20th anniversary, let’s celebrate everything Buffy brought to television. Here are the five biggest ways Buffy changed TV.

1) Buffy put The WB — and the smart teen soap — on the map

Were there teen shows before Buffy? Undoubtedly. Just a few years before Buffy’s debut, My So-Called Life aired a single, glorious season in 1994-’95 and is still one of the best one-season wonders of all time.

But My So-Called Life was self-consciously “realistic,” in a way that teen viewers haven’t always appreciated. The quintessential teen show when Buffy debuted in 1997 was the (then still-running!) trashy fun of Beverly Hills 90210, which had bowed at the dawn of the decade, in 1990. On 90210, as on so many other teen soaps, characters traded romantic partners, emotions frequently shot through the roof, and occasional episodes dealt with Serious Social Issues. It was fun but disposable, a way of talking about the things teens go through without talking about them too seriously.

Buffy found a way to have its teen soap and eat it, too — and it gave rise to an entire network’s voice in the process. The series landed on The WB largely because the network was young, having just launched in 1995, and could afford to take a swing at attracting the teen audience, which TV largely had ignored for decades. (In general, as a mass medium, TV tried to attract as large an audience as possible, which meant that shows ostensibly about teenagers, like Happy Days, were often aimed more at parents with young children.)

And when Buffy turned out to be a hit — especially once it was paired with a new show called Dawson’s Creek midway through its second season — the show remade The WB in its image, dovetailing nicely with a teen-focused movement throughout pop culture that foreshadowed today’s ongoing attempts by corporations to win over fickle millennials.

The late ’90s were the era of Scream and the Spice Girls and the earliest days of YA publishing. And as more and more teen-focused properties caught on, pop culture didn’t merely come to realize that teens had disposable income — it came to realize that teens had a lot of disposable income.

Of course, there had been teen booms in pop culture prior to that moment. What was different with the boom that Buffy helped set in motion was an increase in critical respectability of teen-centric stories. On The WB alone, shows like Dawson’s Creek, Gilmore Girls, and Everwood (all about teens dealing with their emotions in small towns) became critical and audience hits.

And of all of these shows, Buffy wasn’t just the most influential. It was also the best. Critics hailed it, placing it in the No. 1 spot on top 10 lists. It received major awards recognition, including an Emmy nomination for its writing. And when it moved to UPN in its sixth season — because UPN was willing to pay a higher licensing fee than The WB — it helped reestablish that network as well, paving the way for later Buffy-alikes such as Veronica Mars.

2) The show’s voice changed how TV characters talked to each other

Even without Joss Whedon’s involvement, there’s a good chance someone would’ve eventually made a TV show centered on a teen girl superhero. But with Joss Whedon — and his eventually stacked writers’ room — Buffy set itself apart from what a more “typical” teen girl superhero series might’ve looked like, thanks to its specific, incredibly witty voice.

Building off its initial “Valley Girl kills vampires” conceit, Buffy tore out of the gate with pithy dialogue that proved this teen-centric supernatural show had its own particular sense of humor. It didn’t just depend on the usual ’90s slang (see: “[x], much?”), but let its characters be funny, bantering back and forth and making jokes in even the direst of circumstances. The show was clearly in love with language, with arranging words in unexpected ways and delighting in the fizzy alchemy of the resulting scripts.

Though Buffy’s friend Xander (Nicholas Brendon) was the obvious Whedon surrogate — and accordingly had the sense of humor closest to that of Buffy’s series creator — Buffy herself tossed off plenty of jokes and casual witticisms in between destroying her many enemies.

Take the moment in season one when Buffy goes up against ancient vampire the Master and full-on drowns, but is resuscitated (by Xander) to defeat him. “You were destined to die,” the Master sputters at the blonde girl standing defiantly in front of him. “It was written!”

“What can I say?” Buffy shoots back. “I flunked the written.”

Buffy’s tendency to taunt her vampire foes with snark even became a running joke. In season five’s “Fool for Love,” Buffy memorably subverted itself by allowing its title character to get so caught up in her quips that her adversary is able to land a devastating blow.

Though no show could quite replicate Buffy’s particular voice, the series’ “Slayer Slang” inspired shows that weren’t strictly comedies to experiment with their own humor and language. And now that Buffy writers such as Marti Noxon (UnReal), Jane Espenson (Once Upon a Time), and Drew Goddard (Cabin in the Woods, The Martian) have all gone on to other genres and projects, Buffy’s voice has lived on far beyond its own finale.

3) The way Buffy structured its seasons broke new ground for serialization on TV

It might seem weird to modern audiences, but Buffy, despite fighting a monster of the week in nearly every episode, was considered a heavily serialized show when it debuted in 1997. And it only became more serialized as it progressed, especially in seasons six and seven, when it prioritized grand, complicated arcs at the expense of episodic coherency.

In retrospect, Buffy’s chief innovation with regard to serialization would be fairly obvious: Each season had a primary villain, whom Buffy and her friends would confront several times throughout the season. Most episodes would at least check in with the primary villain’s plans, no matter how tenuously connected they were to the main action/monster of the week.

Essentially, this approach was a heightening of the X-Files model, where standalone episodes and episodes linked to that show’s overriding alien conspiracy uneasily shared space right next to each other. Whedon and the Buffy writers’ room simply incorporated the larger arcs more seamlessly. And both Buffy and The X-Files were heavily indebted to ’80s workplace dramas like Hill Street Blues and St. Elsewhere, which blended their characters’ ongoing personal concerns with crimes or diseases of the week. (It’s also easy to spot a hint of the ’80s crime drama Wiseguy — in which an undercover cop pursued one villain per story arc, with multiple story arcs per season — in Buffy’s overall architecture.)

Where Buffy cut its own path was in combining all of those influences to create a model that’s still in use today, largely unchanged. Every season of the venerable monster-hunting show Supernatural, now in its 12th season, uses this model. Lost used it too, but broke its overarching story into smaller pieces and swapped primary objectives (getting off the Island, etc.) for a big villain in each season. And do we need to point out The Walking Dead’s similarity to this storytelling format? Probably not.

But the format is present even in non-genre shows, from Scandal to Justified. Each season, some major crisis or villain dominates the storytelling, and every episode reflects on it somehow, sometimes in a major way and sometimes in a much more minor one. Even the “case of the season” crime drama — which includes shows like The Killing and The Bridge — more or less uses the Buffy format, interpreted in a slightly different way.

Whedon (a longtime comics fan) was heavily indebted to Marvel comics in how he told his story, and his conception of Buffy as a series of “arcs” with main villains is very similar to how the comics industry compiles individual issues into sturdier “trade paperbacks,” which are then sold in bookstores.

When Whedon turned the misbegotten movie Buffy into a TV show, he couldn’t have known that the DVD box set and streaming services would roughly replicate the trade paperback experience for TV fans, but they have.

And his debt to Marvel shines throughout the show, particularly in its wildly inventive plot twists. Characters on Buffy are never one thing. They all flirt with evil. Sometimes they actually become evil. They float in and out of relationships, have their hearts broken, and emerge stronger in the end. Buffy died twice, came back from the dead twice, and mysteriously gained a sister she hadn’t had for the first four seasons in the fifth. (That sister turned out to be the center of a massive magical conspiracy, of course.)

Buffy didn’t just synthesize a bunch of trends into a new way of telling stories — it created the expectation that those stories would be told with bold, splashy colors.

4) Monsters became metaphors — and part of the show’s structure

From the beginning, Whedon envisioned a structure for Buffy that at the time breached a whole new frontier for TV but has since became something of an assumed routine.

Every week, Buffy and her friends ran up against monsters that would in some way tie into the struggles they were facing in their own lives. People who felt invisible might literally become invisible. Seductive preying mantises might make a teenage guy feel less lonely. When Buffy lost her virginity to Angel in season two, his immediate transformation into an evil version of himself made the omnipresent reality of men who turn on a dime once they sleep with someone searingly literal.

And when the world felt like it was ending ... well, for Buffy, that usually meant it was.

For Whedon, this came from wanting to make a high school show in which the horrors of being a teen came to terrifying life, but could be defeated by the end of the episode. And in the years since Buffy left the air, its “monster of the week” structure has endured, even if plenty of shows use it without making literal monsters out of their characters’ emotional arcs.

Grey’s Anatomy, for instance, has spent 13 seasons using the medical horrors of the week as metaphors for its characters’ pressing problems. TV superheroes on The CW’s Flash and Netflix’s Jessica Jones confront weekly villains whose powers are direct manifestations of their greatest insecurities and fears. Even procedurals like Law & Order or Criminal Minds — which have always relied on a “case of the week” structure — have been inspired to tie their disposable perpetrators to the ongoing stories of its main characters.

5) Buffy made for a new kind of feminist action hero

Buffy’s origin story subverts one of pop culture’s most famous tropes. The idea for the series came about when Whedon, a horror movie fanatic, wondered what it might look like to let “that blonde girl who’s always getting herself killed” fight back — and kick serious ass.

So he created Buffy, a former Valley Girl who reluctantly began slaying vampires in her not-so-friendly local graveyards. She was practically unrivaled in both physical strength and steel-willed emotional fortitude but also a far cry from the few and often grim female action heroines who had preceded her (see: Alien’s Ripley). As played by Gellar, Buffy was a chipper, quippy teen who wouldn’t think twice about wearing frosted eye shadow to a vampire hunt. She was funny, smart, frustrated, and flawed.

As comics and YA fans will be quick to attest, Buffy wasn’t pop culture’s first female superhero, not by a long shot. But she was the first to anchor her own TV series, and her success paved the way for others like her.

Also, as a teen girl hero, Buffy inevitably ended up dealing with issues that lay outside the purview of male action heroes — issues like high school clique politics and slut shaming — and the way Buffy addressed them became one of the show’s hallmarks.

Buffy was, crucially, no one’s sidekick. In the words of her fellow prophetic blonde Britney Spears, Buffy was the ringleader; she called the shots. She saved the world and changed television — a lot.