The entire first season was filmed before the first episode went to air, giving them the opportunity to go back and re-shoot various scenes. The scene in the library where Buffy states "it's my first day..." was actually filmed on the last day of shooting after they decided her original performance was too forceful and aggressive. Another scene added to the pilot (to fill in time as it was shorter than expected) was the infamous "you have something in your eye" scene where The Master blinds a vampire who had failed him.
Series creator Joss Whedon wanted to do a musical episode as early as the first season, but the network wouldn't allow him to. When the show switched networks after the fifth season, he was finally able to get his wish, resulting in the episode Buffy the Vampire Slayer: Once More, with Feeling (2001).
Series Creator Joss Whedon has said that the idea for Buffy came from all the horror movies he had seen featuring a helpless young blonde who would almost always be the first to die. He felt she needed a better image.
Although she was not credited by name, one of the executive producers of Buffy the Vampire Slayer (1997) was the country singer Dolly Parton, who had a production partnership (called Sandollar Entertainment) with Sandy Gallin, who had managed Parton's career.
Kali Rocha, who showed up in the sixth season as vengeance demon Halfreck, first appeared in a flashback episode in the fifth season as Cecily, the woman who spurned William, causing him to become the vampire known as Spike. Having already cast Rocha as Halfreck, the writers knew the loyal fans would immediately recognize her, so as an inside joke between them, when Halfreck first saw Spike, she said, "William?" It is debated whether they are the same character.
Originally another actress had been cast as Anya, but backed out after finding out it was only for two guest spots. The role wound up going to Emma Caulfield, and, starting toward the end of the third season, Anya became a regular character throughout the rest of the show's run.
The series is based not on the feature film Buffy the Vampire Slayer (1992), but Joss Whedon's original screenplay, which had been heavily rewritten to be more comedic. The Buffy comic book series adapted the screenplay, bringing the events of the movie in line with the TV show's continuity.
David Fury said in some DVD commentaries that Sarah Michelle Gellar doesn't like to act laughing because she found herself too fake. To tease her, Fury wrote scenes where Buffy laughed whenever he could.
Buffy's birthday was celebrated in the episode first aired on or near 19 January each year. In the first-year episode "I Robot, You Jane", Malcolm brings up Buffy's school records on his computer. In the first view, we see that Buffy was born on 24 October 1980, and that she is a sophomore. The second time we see Buffy's records, her birthday is 6 May 1979, and she is a senior. Joss Whedon finally decreed Buffy's birthday to be 19 January 1981.
Because of the feud with UPN and the WB over Buffy jumping networks, crossovers between 'Buffy' (which was on UPN), and Angel (1999) (which remained on the WB) were prohibited during season six (season three of 'Angel').
Interviewer Will Harris asked why actors from the canceled series Firefly (2002) became characters in the last few seasons of Buffy the Vampire Slayer (1997) and Angel (1999) - referring to Nathan Fillion as Caleb in "Buffy" and to Gina Torres as Jasmine and Adam Baldwin as Marcus Hamilton in "Angel" (as well as Alan Tudyk in Dollhouse (2009)) - and whether Whedon had promised them "work if their show tanked." Whedon replied, "No, you know, I was against it at first. I thought, it'll seem incestuous and weird. But then, they're, like, Joss, nobody saw Firefly. No one will know. You know these actors are great, you know you love working with them, you know you need somebody bigger than life for the role, and, so, get over it. And I did. Rather dramatically." in "Joss for a minute: A brief chat with Joss Whedon," 11/29/2005]
USA ratings for the series over the seven year run: Season 1 - 3.7 million viewers; Season 2 - 5.2 million viewers; Season 3 - 5.3 million viewers; Season 4 - 5.1 million viewers; Season 5 - 4.5 million viewers; Season 6 - 4.6 million; viewers Season 7 - 4.1 million.
Originally, Joss Whedon didn't want either of Buffy's parents to appear as characters on the show. Accepting that that could get complicated, he settled on just having her mother, Joyce, appear in a nearly regular role, while Buffy's father Hank appeared in very few episodes.
In a 6 May 2003 interview by Fred Topel, Alyson Hannigan and Alexis Denisof jokingly talked about the show's death of cast members as the series progressed toward its end. Hannigan said, "Nobody dies on our shows." Denisov said, "Death is insignificant." Hannigan added, "Death is just really a plot twist." This has long since become a joke among fans, but here it is articulated by two actors who knew what would happen in the months between the last season of Buffy the Vampire Slayer (1997) and the fourth season of Angel (1999).
The character Jenny Calendar was originally to have been called Nicki. This was changed to Jenny to avoid confusion on the set, Nicholas Brendon being generally called Nicky by his co-stars. (However, in season 7, the character Nikki Wood was added and appears in several episodes.)
According to visual effects supervisor Loni Peristere, an average episode has 18 to 50 visual effects shots, about 10 percent of the total number of shots. The two most common are vampires morphing into game-face and vampires being dusted. For those, the effects team uses Maya V.4.5 with Stroika, a collection of plug-ins/software, which lets the artists take image maps or photographs and emit particles of the same color and lighting.
The prologue ("In every generation there is a chosen one....") is not used consistently. Two of the first twelve episodes don't use it. During the second season, use of the prologue becomes even more spotty. Anthony Head intones it only during the second season.
The trivia items below may give away important plot points.
During an interview on the National Public Radio program "Fresh Air," Joss Whedon told interviewer David Bianculli that during the first few years Buffy was on the air, he used to frequent internet message boards about the show. On one such board, there was a discussion of what the posters perceived as sexual tension between the characters Buffy and Faith. Whedon posted that he disagreed, that he thought some viewers saw "lesbian subtext behind every corner" and that they just wanted "to see girls kiss." One poster asked Whedon to look at her website, where she had analyzed multiple Faith episodes and systematically laid out the subtext between the two slayers; after that, Whedon returned to the original posting board and apologized, saying that the original posters were absolutely correct about the lesbian subtext between Faith and Buffy.
Epilogue to some of the characters is given in Angel: The Girl in Question (2004). In that show it is said that Buffy and Dawn are living in Rome and Dawn is going to school there in order to learn Italian. This is an in-joke based on Kristine Sutherland who played Joyce Summers on Buffy. She was largely absent from season 4 because she was house-sitting in Italy, partly in order to allow her daughter to go to school there and learn Italian. Now her character's daughters do the same.
The characters of Spike, Oz, Faith, Wesley and Drusilla were all supposed to be killed off, but have ended up living long past their initial storylines. Also, the characters of Jenny and Joyce were supposed to be killed off sooner than they were.
The character of Angel was supposed to stay dead after the season finale of the second season, but the WB network came to Joss Whedon with the desire for a spin off series, so Angel was brought back during the third season to set up his spin-off series Angel (1999).
Although the television show ended with the Season Seven finale, the storyline was continued in a 40-issue series of comic books that tell the story of the continued "Season Eight." The series is published by Dark Horse Comics and produced by Joss Whedon, who was the creator of the original show; many individual issues have been written by Whedon or other writers who had worked on the show, including Jane Espenson, Drew Goddard, Drew Z. Greenberg, Steven S. DeKnight, and 'Doug Petrie'. The first issue was released in March 2007 and (as of mid-2009) issues continue to be released. The Season Eight storyline has Buffy and her friends in charge of a quasi-military worldwide network of slayers (the "potential" slayers who were turned into actual slayers toward the end of the show), with bases in Scotland (run by Xander), England (Giles), Italy (Andrew Wells), and Cleveland, Ohio (Robin Wood). The storyline for all surviving characters continues, with Willow, Xander, and Buffy all dating slayers for varying lengths of time.
Shooting season 3, Kristine Sutherland told Joss Whedon she was planning to leave the series. Whedon agreed partially, making her appear only in 5 episodes on season 4 but also said he'd need her on season 5 because her character was going to be killed.
According to Nicholas Brendon, he and Sarah Michelle Gellar proposed a storyline for season seven where Xander and Buffy get together romantically. Their idea was shot down, and they continued with the Buffy-Spike relationship.
Originally, the third member of the sixth season's nerdly Trio was to be Tucker, villain of Buffy the Vampire Slayer: The Prom (1999). Plans fell through with that, so the writers replaced him with Andrew, Tucker's younger brother.
The character played by Julia Lee who first appeared in "Lie to Me" (episode 2.7) as the self-named "Chanterelle," reappeared under several different names over the runs of both Buffy the Vampire Slayer (1997) and Angel (1999). At the start of her next appearance on "Buffy" ("Anne," episode 3.1) she had changed her name to Lily; during that episode, she relates to Buffy one instance about her past where she had joined a cult that renamed her "Sister Sunshine;" and at the end of the episode, Buffy gives her both a job and her newest sobriquet, "Anne" (Buffy's real middle name). By the time the character first appears on "Angel," she has kept "Anne" as her first name and added the last name "Steele" to it. Although it is never mentioned onscreen, the original teleplay for "Lie to Me" indicated that her original name was Joan (which is also the name that Buffy chooses for herself when she can't remember any autobiographical details in "Tabula Rasa").
Many actors were able to reappear on the show, despite the fact that their characters were killed off. Among those who reprised their roles, once their characters were killed or murdered, were Mark Metcalf as The Master, Robia LaMorte who appeared several times after the character of Jenny was killed, Azura Skye, Danny Strong, Lindsay Crouse and Kristine Sutherland. Darla, played by Julie Benz, was killed during the first season, yet not only did the character appear in flashbacks, but she was also later resurrected from death on the sister-show Angel (1999).
Throughout the series, every character that owns the "Magic Box" shop ended up brutally murdered, usually by a vampire: An unnamed clerk in the second season, a female unnamed clerk in the third one, Mr. Bogarty in Season 5, Anya Jenkins in the final season (slashed by one of the Bringers, minions of the First Evil), and at last Giles (killed by a possessed Angel) in the Season Eight comic book.
Almost all of the main characters have been demons at one point in the show: Buffy was a vampire in Buffy the Vampire Slayer: Nightmares (1997); Xander was a vampire in Buffy the Vampire Slayer: The Wish (1998) along with Willow whose vampire self also appeared in Buffy the Vampire Slayer: Doppelgangland (1999). Angel and Spike have always been vampires. Cordelia becomes a demon in "Angel", the Series. Oz is a werewolf. Anya was a demon when she first appeared on the show and Giles turned into a demon in season 4. Riley, Tara and Dawn are the only main characters who were never demons, although Dawn used to be some sort of mystical Key-thingy up until season 5 and Tara's family had her convinced she was one until Buffy the Vampire Slayer: Family (2000).
All of the main trio (Buffy, Xander and Willow) had relationships with other vampire slayers throughout the series. Willow started dating Kennedy (Iyari Limon) in the seventh season, Xander lost his virginity to Faith (Eliza Dushku) in Season Three and dated a Slayer named Renee in the Season Eight comics, where Buffy had a sexual encounter with Satsu, a Japanese Slayer.