On the genre-busting television show Buffy the Vampire Slayer, the heroine saved the world—a lot—over the course of seven seasons. Buffy premiered on the WB 21 years ago today; here are a few things you should know about the show. (And this is just the tip of the stake.)

1. THE SHOW IS A SEQUEL OF SORTS TO A MOVIE.

In the late ‘80s, writer Joss Whedon had an idea for a movie that would subvert the horror genre. “I had seen a lot of horror movies, which I love very much, with blond girls getting killed in dark alleys, and I just germinated this idea about how much I would like to see a blond girl go into a dark alley, get attacked by a monster and then kill it,” he said. “And that was sorta the genesis for the movie, Buffy the Vampire Slayer.” The movie, penned by Whedon and directed by Fran Rubel Kuzui, hit theaters in 1992. It starred Kristy Swanson as Buffy, Donald Sutherland as her watcher Merrick, and Luke Perry as her love interest, Pike (David Arquette also starred as Pike's best friend-turned-vampire Benny). But the film was different from what Whedon had originally intended. “My original script for the movie was kind of dark and scary and it was comedic, but the final product was much more a broad comedy,” he said.

A few years later, the rights holders approached Whedon about making a TV show out of his creation. He wasn’t sure it would work, but “I started to think about it and I came up with the notion of playing all sorts of horror movies in high school and making them metaphors for how frightening and horrible high school is,” he said. “With the show, I kinda wanted to get back to the roots of genuine horror, but with a lot of comedy and a lot of edge and a lot of self reflective sort of examination of horror. But at the same time, get genuinely creepy and hopefully genuinely moving.” And the TV version of Buffy was born.

2. KATIE HOLMES AND RYAN REYNOLDS COULD HAVE STARRED ON THE SHOW.

Could you imagine Katie Holmes as Buffy and Ryan Reynolds as Xander? According to a 2000 biography, before she was Dawson’s Creek's Joey Potter, Holmes was offered the role of the slayer, but turned it down to go to high school. Reynolds refused the role of Buffy’s wisecracking sidekick. "I love that show and I loved Joss Whedon, the creator of the show, but my biggest concern was that I didn’t want to play a guy in high school," Reynolds told The Star in 2008. "I had just come out of high school and it was f***ing awful."

3. GILES WAS THE FIRST ROLE CAST.

According to casting director Marsha Shulman, “Anthony Stewart [Head] was the first person that got cast on the first day we started casting. He was just it.”

Many other actors who read for the part, Whedon said, made Giles too stuffy, but Head’s take was a little sexier. “Tony Head was one of the few people that we saw and instantly knew right away that nobody else was going to play that part,” Whedon said. “He embodied it perfectly.”

4. SARAH MICHELLE GELLAR AND CHARISMA CARPENTER SWAPPED ROLES.

Gellar auditioned for the role of Sunnydale High queen bee Cordelia Chase before eventually being cast as Buffy. “At the time, we were all trying to find our way to make the show something, its own thing apart from the film,” Schulman said in The Watchers Guide. “We didn’t think of Sarah as Buffy because we thought she was too smart and too grounded and not enough of a misfit in a sense, because Buffy was this outsider. How could Sarah be an outsider? She’s so lovely. So we brought her in as Cordelia, and she was fantastic as Cordelia. Then we went to the network, they knew that Sarah was a star from her previous work, and that she could be Buffy, and that we could do that Buffy.”

Carpenter, meanwhile, auditioned for Buffy before being cast as Cordelia. “I think that the way it turned out is the way it was meant to have turned out,” Carpenter told the BBC. “I’m extremely pleased that I wound up with the character that I have for a myriad of reasons. ... I don’t know that I would have been ready for that kind of fame if I’d gotten Buffy. So, I think [Buffy] went to the right person.”

5. WILLOW WAS RECAST AFTER THE PILOT WAS SHOT.

Willow, science geek and Buffy’s best friend, was an exceptionally tough part to cast. “We had actually cast someone else in the pilot. It just didn’t work,” Shulman said. “When we got picked up, we always felt that we were going to start again and look for another Willow.”

“I was determined that we wouldn’t have the supermodel in horn rims that you usually see on a TV show,” Whedon said. “I wanted somebody who really had their own shy quirkiness. While the network and I were looking for people, Alyson Hannigan slipped under our radar. She came in and we didn’t really know that she was going to be the guy, and then when she read for the network we were just blown away. She brings so much light and so much tenderness to the role, it’s kind of extraordinary.”

6. DAVID BOREANAZ WAS DISCOVERED BY THE CASTING DIRECTOR’S FRIEND.

Whedon, the network, and the casting director saw a number of guys read for Buffy's eventual boyfriend (and vampire!) Angel before David Boreanaz auditioned. “The breakdown said the most gorgeous, mysterious, fantastic, the most incredible man on the face of the earth,” Shulman said. “I think I saw every guy in town. It was the day before shooting, and a friend of mine and called me and said to me ‘You know, there’s this guy that lives on my street who walks his dog every day and I don’t know what he does but he has all the things you’re describing.’ And the minute he walked in the room, I wrote down on my notes: This is the guy.”

Still, despite the fact that Boreanaz gave “very good read,” Whedon wasn’t sold on him. “He wasn’t exactly my type,” he said. “I wasn’t sure we necessarily had the guy here until I asked the women in the room, who had turned into puddles the moment he walked in. I had to defer to them—they seemed to know better than me, and thank god I did, because David turned into a great star and a very solid actor.”

7. THE FIRST VERSION OF THE THEME SONG WAS A DUD.

Whedon wanted the credits sequence—which begins with “this scary organ and then devolves instantly into rock 'n roll”—to spell out for viewers exactly what the show was about: “Here’s a girl who has no patience for a horror movie, who is not going to be the victim, is not going to be in the scary organ horror movie,” he said. “She’s going to bring her own youth and rocking attitude to it.”

Dissatisfied with an early version of the theme, Whedon opened it up in a contest of sorts to local indie bands. It was Hannigan who suggested Nerf Herder; the band ultimately wrote and recorded the show’s theme. “They created the show and were filming the first season and the people there ... hired some fancy pants Hollywood guy to write the theme song and they didn’t like it; they wanted something more rocking, I guess,” Nerf Herder’s lead singer, Parry Gripp, said. “So they asked a bunch of local, small time bands who they could pay very little money to come up with some ideas and they liked our idea and they used it. And the rest is history!”

The band rerecorded the theme in the second or third season because the first recording was a hasty affair, and the song went off-tempo in the middle, Whedon said.

8. THE SHOW SHOT IN A WAREHOUSE—AND AT ACTUAL SCHOOLS.

In the beginning, Buffy didn’t have much of a budget, so instead of shooting on a soundstage, the crew used a huge warehouse in Santa Monica, California. “We were very much on a tight budget,” Whedon said. “This hall you’ll see a lot of in the first 12 episodes. It is the entire school. We only had the one hall, so we use it over and over again. It’s really kind of sad, actually.” The outside of the warehouse also doubled as the entrance to Sunnydale’s only club, The Bronze. “When we designed the club, we put the door to the club on the outside of the actual warehouse so that we could go in from the outside because that would give it real life and make it very realistic,” Whedon said. “And of course we did it just once, and then once more in the third season, because you have to wait until night to shoot, go in and out and light it, and it’s just enormously complicated.”

Torrance High School in Los Angeles subbed in for the exterior of fictional Sunnydale High. It’s a popular spot for film and TV; you might also recognize it from Beverly Hills, 90210, The Secret Life of the American Teenager, 90210, She’s All That, Not Another Teen Movie, and more. And when Buffy went to college, most of Sunnydale University was shot in the warehouse, but some parts of the first episode of the fourth season were shot at UCLA.

9. THERE WAS A REASON FOR THE VAMPIRES’ CREEPY FACES—AND THE "DUSTING."

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In the Buffy movie, the vampires looked like regular people with sharper teeth and paler skin. But for the show, Whedon wanted to increase the sense of paranoia by making the vampires resemble normal people until it’s time to feed—at which point, they transform into monsters. But there was another reason, too. "I didn't think I really wanted to put a show on the air about a high school girl who was stabbing normal-looking people in the heart,” Whedon said. “I thought somehow that might send the wrong message, but when they are clearly monsters, it takes it to a level of fantasy that is safer."

Getting into vamp mode—which required a prosthetic that fit from the forehead down to the bottom of the nose—took about an hour and 20 minutes. “It can be tedious,” David Boreanaz said in 1998, “and taking it off is the worst part, because you have to sit there and you just want to rip the damn thing off—but you can’t, because you’ll take a piece of your skin with you. It has to be removed very delicately. But the end result is definitely worth it.”

The film also had vampire bodies lay where they fell after they were staked. But Whedon had different ideas for the show. “It was a very conscious decision to have [the vampires] turn to dust, clothes and all, because I didn’t think it would be fun to have 15 minutes of let’s clean up the bodies after every episode,” he said. The show’s visual effects artists worked on and refined the technique over the seasons.

10. THE CREATORS DREW ON EXISTING VAMPIRE LORE FOR THE SHOW.

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But they didn’t use everything. Vampires don’t fly on Buffy or turn into bats because the show didn’t have the money and Whedon thought it looked silly. Other elements of vampire lore, however, were used: Vampires don’t have reflections; they can’t enter a house unless they’re invited; they’re vulnerable to garlic, crosses, sunlight, fire, and holy water; and they can be killed by beheading or via a stake through the heart.

11. GELLAR HAD SOME PROBLEMS WITH THE DIALOGUE.

The show was famous for its “Buffyspeak,” which was partially inspired by California Valleygirl-isms and how Whedon and the other writers spoke. For Gellar, though, that dialogue sometimes was an issue. “Joss has his own sort of language that’s difficult for us mere mortals to understand,” she said in 1998. “I grew up in New York. We didn’t have Valley girls, and constantly, I’m asking him ‘What does this mean? I’m not quite sure.’ There’s a very funny story about [my audition] where the first line is ‘What’s the sitch?’ And there I go walking in, and my first [question was,] ‘What does this mean?’ No idea it meant situation. Talk about blowing a job instantly.”

12. HERE’S WHERE YOU’VE SEEN SEASON ONE’S BIG VILLAIN BEFORE.

Underneath all of the Master’s vampy makeup is actor Mark Metcalf, who has appeared in Animal House (he played Doug Neidermeyer) and Seinfeld (he played The Maestro), among many other films and television shows. “Most of the guys we read came in and gave us villain villain villain in a very unimaginative way,” Whedon said. “Mark’s not that character, he’s just sly. He undercut all of the villainousness with real charm.”

13. THE CAST AND CREW HATED THE LIBRARY SCENES.

Head delivered much of the show’s expository dialogue in the library—and cast and crew alike came to dread those scenes. “He’s brought so much to all these really tough speeches, giving them life where they had very little because they’re full of so much information,” Whedon said. “When we finally blew up the school at the end of season three and were in the library for the last time, everybody breathed a great sigh of relief because these became the bane for us when we were filming, to go back into this space and talk yet again about what the peril was going to be.”

14. DARLA WAS SUPPOSED TO DIE IN THE SECOND EPISODE.

The vampire (played by Julie Benz) was supposed to expire at the end of “The Harvest” after Willow doused her with holy water, but Whedon kept her alive because he thought Buffy and Angel's romance would be more interesting if it was a triangle; Darla, of course, was Angel’s sire. She was eventually killed in episode seven, but would continue to pop up in other episodes—and in the spin-off show, Angel—from time to time.

15. GELLAR AND BOREANAZ WOULD EAT GROSS STUFF BEFORE KISSING SCENES.

In a 2002 interview with The Independent, Gellar called love scenes “the unsexiest thing in the world.” What she and Boreanaz did beforehand couldn’t have made it any sexier. “[We] were the worst,” she said. “We would do horrible things to each other. Like eat tuna fish and pickle before we kissed. If he had to unbutton my shirt or trousers I would pin them or sew them together to make it as hard as I could. Once I even dropped ice cream on him.”

16. THE SHOW BUILT ITS OWN GRAVEYARD.

In the first season, Buffy shot in a graveyard in Hollywood. “It meant going out all night, until sunrise, a lot of times,” Whedon said. “That was back when we had the energy for that kind of thing.” Starting in the second season, they created their own graveyard in the warehouse’s parking lot. “It made our lives a whole lot easier, but it doesn’t give you the scope that you get from [the Hollywood graveyard],” Whedon said. “It’s a really beautiful place. Looks great.”

"We poured in kerb, back-filled it with dirt and planted grass and lots of trees and stuff and that’s our graveyard set," production designer Carey Meyer told the BBC. "The majority of our cemetery stuff actually takes place in that little tiny parking lot. At night, with a couple of headstones in the background with all the trees and such, you can really cheat to make it look quite large."

17. WHEDON HAD AN INTERESTING NICKNAME FOR GELLAR.

At a cast reunion in 2008, Whedon revealed—to Gellar's surprise—an odd nickname for her, borne from the fact that she dealt with so much pain on screen. "David [Greenwalt] and I used to crow, when we realized what Sarah could do," he said. "We used to call her Jimmy Stewart, because he was the greatest American in pain in the history of film." Gellar laughed and said, "I never knew that!"

18. AT LEAST TWO ACTORS PLAYED MORE THAN ONE VILLAIN.

Brian Thompson, who played vampire Luke in the first two episodes, returned in the second season to play The Judge. “Quite frankly, we were in a hurry,” Whedon said. “We already had his face cast and we knew he could put makeup on and give us a good performance.” Camden Toy, meanwhile, played a number of villains, including one of the Gentlemen in “Hush” (season four), a skin-eating demon called Gnarl in “Same Time, Same Place” (season seven), and Ubervamp Turok-Han (throughout season seven).

19. THE WRITERS HAD THEIR OWN TERM FOR PLOT-MOVING DEVICES.

It was coined by writer David Greenwalt. “A lot of this stuff is based on myth and horror movies, and a lot of it made up for our convenience,” Whedon says. “At one point, when we were trying to figure out exactly what Buffy would be trying to do [in the first episode], Greenwalt just shouted out ‘For God’s sake, don’t touch the phlebotnum in Jar C!’ We have no idea to this day what it was supposed to mean, but it became our word for the vague mystical thing—such as the master’s cork in the bottle theory—so phlebotnum is our constant on the show.”

20. WHEDON WROTE THE LARGELY DIALOGUE-FREE EPISODE “HUSH” TO CHALLENGE HIMSELF.

Season four’s tenth episode, “Hush,” features creepy villains called The Gentlemen, who come to Sunnydale and steal the residents’ voices ... so that no one can scream when the monsters cut out their hearts. There are only 17 minutes of spoken dialogue in the 44 minute episode. Whedon wanted to do a largely silent episode because he felt like he was phoning it in. “I had fallen into the ‘people a-yakkin, I can sort of do this without really thinking about it’ style of directing, and I wanted to curtail that in myself,” he said. “On a practical level, the idea of doing an episode where everybody loses their voice presented itself as a great big challenge because I knew that I would literally have to tell the story only visually, and that would mean that I couldn’t fall back on tricks. I wanted to do something harder.” Though Whedon was terrified that he wouldn’t be able to pull off the episode, it was well received by critics, and is a favorite of fans and the series’ stars alike.

21. THE GENTLEMEN WERE INSPIRED BY A DREAM.

A version of Buffy’s creepiest villains first appeared in a dream of Whedon’s; they floated toward him while he was in bed. “What I was going for was very specifically a very Victorian kind of feel, because that to me is very creepy and fairytale-like,” Whedon said. He created a drawing, which he delivered to makeup supervisor Todd McIntosh and John Vulich at Optic Nerve, the special effects house that created the prosthetics for the show. “I was drawing on everything that had ever frightened me, including the fellow from my dream, Nosferatu, pinhead, Mr. Burns—anything that gave that creepy feel,” Whedon said. “We get into a lot of reptilian monsters and things that look kind of like aliens, and what I wanted from these guys was, very specifically, fairy tales. I wanted guys who would remind people of what would they were scared of when they were children.”

Whedon’s ultimate hope was that kids of a certain generation would be as traumatized by the Gentlemen as he was by the Zuni Doll from Trilogy of Terror. The team cast mimes and actors who had done creature work—like Doug Jones—to play the Gentlemen.

22. THE HARDEST CHARACTER FOR WHEDON TO KILL OFF WAS BUFFY'S MOM.

One of Buffy's most critically acclaimed episodes is season five's "The Body," in which the slayer's mom, played by Kristine Sutherland, dies of natural causes. Whedon said in a 2012 Reddit AMA that Joyce was the toughest character for him to kill. He did the episode, he said in DVD commentary, because "I wanted to show not the meaning or catharsis or the beauty of life or any of the things that are often associated with loss, or even extreme grief, which we do get in the episode. But what I did want to capture was the extreme physicality, the almost boredom of the very first few hours. I wanted to be very specific about what it felt like the moment you discover you’ve lost someone. And so what appears to many people as a formal exercise—no music, scenes that take up almost the entire act, if not the entire act, without end—is all done for a very specific purpose, which is to put you in that moment of dumbfounded shock, that airlessness of losing somebody."

The moments after Buffy discovers her mother dead on the couch were done in a single take, which Whedon had Gellar perform seven times (the actress has called the episode one of her favorites). "The cameraman had the camera on his shoulder the whole time and was running around," Whedon said. "It wasn’t a steadicam—he had no harness because I wanted that urgency of handheld, that you’re in the moment of it. It’s an extraordinary piece of acting from Sarah ... to go from the extremity of first finding her, the helplessness of not knowing what to do. All the things that Sarah had to go through in this, she had to go through many, many times. And every take was extraordinary."

23. ONE SHOT IN "THE BODY" WAS INSPIRED BY DIRECTOR PAUL THOMAS ANDERSON.

One shot in "The Body" follows the coroner after he examines Joyce's body out to where Buffy waits with her friends in another single take. "I am a huge Paul Thomas Anderson fan," Whedon said, "and I had been watching Magnolia excessively before I shot this. So these endless tracking shots probably owe something to that. What can I say, I’m a hack. But what I was really trying to get at here was, again, the reality of the space. I wanted to see Joyce very clearly, and then I wanted to walk all the way over to where Buffy was, where her loved ones were, so that you understood she was down the hall, she was really there. We weren’t on a different set." Whedon gave kudos to production designer Carey Meyer for building sets that would let him get those long takes.

24. GELLAR KNEW WHAT WOULD HAPPEN IN SEASON FIVE WELL IN ADVANCE.

Several moments in the final episode of season three foreshadowed two major events in season five: Namely, that Buffy would get a sister (Dawn, played by Michelle Trachtenberg) and that the slayer would die at the end of season five. "I’ve actually known the [plot of the] entire last season for about three years," she told the BBC. "There was a dream sequence that Buffy had with Faith. Faith had a riddle, and it was something like 'Little Miss Muffet, sitting on her tuffet,' counting down from whatever the numbers were, and I went to Joss to ask what it meant. That’s when he explained to me that I was going to have a sister, that Dawn, the character of Dawn, would be coming on the show. I think that’s exactly when I became aware also of what the future plans were."

Why manufacture a sister out of thin air? "Part of the mission statement was, let’s have a really important, intense emotional relationship for Buffy that is not a boyfriend," he told Salon. "Because let’s not have her be defined by her boyfriend every time out of the bat. So, Season 5, she’s as intense as she was in Season 2 with Angelus, but it’s about her sister. To me that was really beautiful."

25. SEASON SIX WAS THE TOUGHEST FOR GELLAR.

After the fifth season, Buffy moved from the WB to UPN and resurrected its heroine for the sixth season—which was darker in tone (and more controversial) than any season before it. "It was definitely tough for me," Gellar said at a Paley Center event in 2008. "It's so hard to separate myself from her, so it was tough for me to see these situations and say 'But Buffy wouldn't do this.' ... I know Joss and Marti both had to talk me off a ledge a couple of times because it just felt so far removed from me at the time, and maybe that was the point. Maybe I was struggling the same way she was struggling to find out who she was. It just felt so foreign to me. ... We love her, and I think it was hard for all of us to watch her suffer. ... It was a tough time. And I think that's what came through in the end, and that was great. When Buffy herself resurfaced, we sort of found our voice again."

26. WRITER/PRODUCER MARTI NOXON HAS A CAMEO.

She’s the lady with the parking ticket in “Once More, With Feeling.”

27. GELLAR CALLED THE MUSICAL EPISODE “DAUNTING.”

“I’m a perfectionist, I come from a long line of lots of preparation, and certainly that was not the case with this,” she said. “If I had my druthers, we would have gotten it about two years ago and been in classes for a year and a half, maybe six weeks of rehearsals? Instead of four days.” At a Paley Center event in 2008, Gellar admitted to “begging” to be let out of it. “I begged for Buffy the rat,” she said. “I kept thinking, ‘Bring the rat back.’”

28. STONE TEMPLE PILOTS’ LEAD SINGER WAS A FAN.

Scott Weiland reportedly became a fan while watching the show in prison. Gellar, who later appeared in the band’s music video for “Sour Girl,” had a theory about why the show was so popular among prison inmates: “Hot chicks doing battle. It's like acceptable porn.”

29. GELLAR KNEW THE SHOW WAS OVER BEFORE THE REST OF THE CAST.

In the March 7, 2003 Entertainment Weekly cover story, Gellar announced that Buffy was coming to an end after seven seasons. "I love this job, I love the fans," she said. "I love telling the stories we tell. This isn't about leaving for a career in movies, or in theater—it's more of a personal decision. I need a rest. Teachers get sabbaticals. Actors don't." The rest of the cast found out the day the story hit stands. “I was devastated," Hannigan said in 2013. "I was just very shocked.”

30. BUFFY’S ADVENTURES CONTINUE IN COMIC BOOKS.

A number of writers who worked on the TV show have also worked on the comics. Even James Marsters, who played vampire Spike on the show, wrote a comic about his character. "I was at the San Diego Comic Con and I was describing an idea that had been kicking around my head for a long time to [artist] George Jeanty, who draws a lot of the Buffy comic books," Marsters told io9. "And he thought that it was a fabulous idea and that I should definitely get in touch with [Dark Horse editor] Scott Allie. He made the phone call and then I pitched it to Scott over the phone and Scott liked it a lot. It's a story that was going to try to be made into a Spike movie years and years ago."

31. THERE WAS TALK OF AN ANIMATED SERIES.

Whedon and the show's other writers produced seven scripts for an animated Buffy series, which would have taken place during the show's first three seasons and been voiced by the cast. Sadly, no one wanted the show. "They were really fun to write," Whedon said. "We could not sell the show. We could not sell an animated Buffy, which I still find incomprehensible."

32. THE SHOW SPAWNED ACADEMIC COURSES...

A number of colleges and universities offer courses on the show; they're called "Buffy Studies." People have written books and held conferences dedicated to discussing the themes of the show and presenting papers on it. According to the Los Angeles Times, attendees at a 2004 Buffy conference "were presenting 190 papers on topics ranging from 'slayer slang' to 'postmodern reflections on the culture of consumption' to 'Buffy and the new American Buddhism.' There was even a self-conscious talk by David Lavery, an English professor at Middle Tennessee State University, on Buffy studies 'as an academic cult.'"

An informal study conducted by Slate in 2012 showed that, when it comes to pop culture in academia, Buffy is number one: "More than twice as many papers, essays, and books have been devoted to the vampire drama than any of our other choices—so many that we stopped counting when we hit 200."

33. ... AND A BOOK OF SLANG.

Publisher's Weekly called Slayer Slang: A Buffy the Vampire Slayer Lexicon "a strange marriage of a fan guide and a linguistics textbook." Said The Kansas City Star: "If you're curious about the word 'ubersuck,' or just want to remember which episode you first heard it in, this is the place to look. As Buffy would say, it is not uncool."

BONUS: RARE BEHIND-THE-SCENES FOOTAGE

During the second season, Pruitt filmed behind-the-scenes footage of the cast goofing off and getting into makeup, the stunt crew at work, and some of the show’s most iconic sequences. You can watch it above.

Additional sources: DVD commentary; The Watcher's Guide.

All images courtesy of Getty Images unless otherwise noted.

This piece originally ran in 2014.