Buffy's prophetic dreams gave several hints about Dawn long before her arrival. In 'Graduation Day, Part 2', season 3, dream Faith tells her 'little sis' is coming', and in 'Restless', season 4, dream Tara warns her 'Be back before Dawn'.

There have been several lines throughout the series have referred to Tuesday ('There's a demon trying to destroy the world and it's just another Tuesday night in Sunnydale' in Revelations and 'Dawn's in trouble. Must be Tuesday' in Once More With Feeling). These are references to the fact that, in the USA, Buffy is aired on a Tuesday.

Many elements of Xander's dream in 'Restless', season 4, were seen again in the season 6 episode 'Tabula Rasa'. In the dream, Spike wears a tweed suit and tells Xander he's in training to be a Watcher (Giles adds "Spike's like a son to me."), also mentioning 'A shark, but on land. A land shark'. In 'Tabula Rasa' Spike is under threat from a loan shark (literally a shark), disguises himself in a tweed suit and after a spell gone wrong believes he might be Giles' son.

In the episode where we learn about Anya's past, there is a flashback to the "Once More With Feeling" episode. Just before Anya closes the door, if you listen very carefully you can hear a prequel to the Mustard Song. Once again it is sung by David Fury and I believe Marti Noxon sings the female part as a prequel to her parking ticket song, and sounds a bit like "Oh no. Mustard on my shirt," "Mustard, I'll never get it out." "My favorite red shirt." "Dryclean it.""How could you serve..." "Mustard."

The 'Grrr Arrrg' monster at the end of each episode (ie. the mascot for Mutant Enemy Inc.) is something that alot of people watch through the credits to see. But if you watch at the end of 'Becoming', he walks past and says 'Boo hoo, I need a hug'...and at the end of 'Once More With Feeling' he sings his 'Grrr Arrrg'...and in the Episode 'Bargaining Pt. 1' Tara gives Giles a small monster as a goodbye present, 'Something to remind you of Sunnydale...' and then goes 'Grrr Arrrg'....Ain't little monster's grand. Also at the end of the Christmas episode where Angel tries to kill himself, the monster is wearing a santa hat, and, at the end of the graduation episode, the monster is wearing a mortar board.

There are three actors who have the rare accolade of having appeared in the three Mutant Enemy shows: Buffy, Angel and Firefly. They are Jonathan M. Woodward who played the vampire Holden Webster in the Buffy episode 'Conversations With Dead People', Carlos Jacott who played Ken in 'Anne' and Andy Umberger who plays recurring vengeance patron D'Hoffryn.

Buffy's chums are regularly referred to as 'The Scooby Gang' which is funny, because Sarah Michelle Gellar actually went on to become an original Scooby as Daphne in Scooby-Doo, the movie.

Sunnydale High School (seasons 1-3) is the same high school that was in Beverly Hills, 90210 (West Beverly High), and the movie Clueless. Its real name is Torrance High located in Torrance, CA.

Nicholas Brendon, who plays Xander, in real life has a stuttering problem and can overcome it by knowing what he's going to say: e.g. scripted, rehearsed material. He said in an interview that he has slowly over the years gotten over the stuttering, but has to work hard at his craft at learning exact lines and rehearsing them over and over again. He doesn't do a lot of live interviews because of this.

Giles' kettle is used twice as an ironic sound effect to show the tension, first when Buffy returns at the start of Season 3 and again in "Revelations."

As Spike, James Marsters' English accent was so convincing, a lot of crew members weren't aware that he's an American.

Oz's band, Dingoes Ate My Baby, takes its name from the headline of a 1980's Australian newspaper. A woman claimed that dingoes were responsible for the disappearance of her baby and was subsequently accused of murder, but later acquitted.

Joss Whedon also wrote the 1992 "Buffy" film. Because of the dramatic differences between his screenplay and the finished film, he doesn't consider it canon as established by the TV series. In fact, the series isn't based on the completed movie at all: it's based instead on the screenplay Whedon initially wrote.

While Joss Whedon considers the 1992 movie non-canon, two characters were carried over: Buffy herself (obviously), and her first Watcher, Merrick. Merrick only made one appearance on the show, through a flashback, and was played by Richard Riehle; in the film, he was played by Donald Sutherland.

In 2004, Adam Busch (Warren Mears) began dating Amber Benson (Tara). Ironically, it was Warren who killed Tara in season 6.

Buffy and Willow were the only characters who appeared in every episode. Because it would have been difficult to incorporate a storyline for him, Xander is missing only from "Conversations With Dead People."

Once Spike appeared on the show, Billy Idol's punk-rocker look became a running gag. Numerous times, Spike claimed that he invented the look, and Idol stole it from him.

Nathan Fillion auditioned for the role of Angel. Fillion later appeared as Caleb in the show's final season, and played Malcolm Reynolds on Joss Whedon's "Firefly."

Before production began, an idea popped up that Buffy would be able to identify a vampire solely by their outdated clothes. While this idea was eventually abandoned, it was toyed with in "Welcome to the Hellmouth" when Buffy sees Willow talking to a vampire in 70s-style dress with his sleeves rolled up and his collar upturned.

A lot of the Scooby Gang's dialogue was based on how Joss Whedon really talks.