In order of character appearances:
- Sarah Michelle Gellar as Buffy Summers (22/22)
- Nicholas Brendon as Xander Harris (22/22)
- Alyson Hannigan as Willow Rosenberg (22/22)
- Anthony Stewart Head as Rupert Giles (22/22)
- Marc Blucas as Riley Finn (20/22) (Does not appear in "Living Conditions" and "The Harsh Light of Day")
- James Marsters as Spike (18/22) (Does not appear in "The Freshman," "Living Conditions," Fear, Itself," and "Beer Bad")
- Seth Green as Oz (8/22) (Does not appear in "The Initiative" to "Where the Wild Things Are," "The Yoko Factor," and "Primeval")
In order of character appearances:
- Emma Caulfield as Anya Jenkins (15/22)
- Amber Benson as Tara Maclay (12/22)
- Leonard Roberts as Forrest Gates (12/22)
- Bailey Chase as Graham Miller (10/22)
- Lindsay Crouse as Maggie Walsh (9/22)
- George Hertzberg as Adam (8/22)
- Kristine Sutherland as Joyce Summers (5/22)
- Adam Kaufman as Parker Abrams (5/22)
- Mercedes McNab as Harmony Kendall (4/22)
- Paige Moss as Veruca (3/22)
- Jack Stehlin as Francis Angleman (3/22)
- Phina Oruche as Olivia Williams (3/22)
- Conor O'Farrell as Colonel McNamara (3/22)
- Dagney Kerr as Kathy Newman (2/22)
- Eliza Dushku as Faith Lehane (2/22)
- Jeff Ricketts as Weatherby (2/22)
- Kevin Owers as Smith (2/22)
- Chet Grissom as Clark (2/22)
- Alastair Duncan as Collins (2/22)
- David Boreanaz as Angel (2/22)
- Jason Hall as Devon MacLeish (1/22)
- Elizabeth Anne Allen as Amy Madison (1/22)
- Andy Umberger as D'Hoffryn (1/22)
- Ethan Erickson as Percy West (1/22)
- Robin Sachs as Ethan Rayne (1/22)
- Saverio Guerra as Willy the Snitch (1/22)
- Harry Groener as Richard Wilkins (1/22)
- Danny Strong as Jonathan Levinson (1/22)
- Armin Shimerman as Principal Snyder (1/22)
- Sharon Ferguson as Sineya (1/22)
Season Four begins with Buffy and Willow enrolling at UC Sunnydale, while Xander begins his working life. While the first three seasons dealt metaphorically with adolescent struggles, their post-high school life now deals with issues of leaving home, redefining relationships, and adapting to more responsibilities and social pressures. UC Sunnydale sits not on a Hellmouth, but a top-secret military installation called The Initiative. Special-ops soldiers pose as teachers, students, and fraternity brothers. The Initiative is headed by Maggie Walsh, Buffy and Willow’s Psychology professor. Riley Finn, with whom Buffy eventually finds a loving relationship, is Walsh’s teaching assistant by day and her protégé in the Initiative at night. Buffy and Riley strive to protect their secret identities from each other.
Though the Initiative appeared at first to be a well-meaning anti-demon operation, it is soon revealed that tests and operations are performed on supernatural beings. Among other things, the Initiative has combined demons, humans, and cybernetics into a prototype super-creature, Adam. An unwitting Buffy tried to integrate her work with that of the Initiative before finding herself in traps set by Walsh. Adam kills Maggie before escaping the Initiative. He masterminded a plan to create a third race, bio-mechanical demonoid creatures like him who would replace humans and demons. Riley discovers that the authority figures he had unquestioningly accepted are not so trustworthy after all.
Season four saw the return of the vampire Spike as a regular character, neutered by the Initiative with a microchip in his brain that prevented him from harming human beings. Spike was now one of the most morally ambiguous characters on the show.
Meanwhile, Oz departs as Willow develops a romantic relationship with fellow Wiccan Tara. Faith wakes up from her coma, and eventually escapes to Angel series. As Buffy and her friends grow apart, they eventually must reunite to defeat Adam through a spell that combines all of their powers into Buffy’s body. The Initiative is destroyed by the demons during the battle.
The main antagonist of this season was Adam.
Behind the scenes
- This season had the most crossovers with Angel series.
- Season Four earned the series an Emmy Award “cinematography for a single camera” nomination for the critically acclaimed episode "Hush," as well as a “hairstyling” nomination for "Beer Bad."
- Joss Whedon has stated that, in season four, “the loss of Angel actually made things easier, because it meant new places to go. What had become tough was wringing new changes out of that relationship. By season four we were into mission statements. What we said was this is the first year of college. The first year of college is about being able to do whatever the hell you want and completely losing yourself, trying on new identities and changing. Exploring sexuality, exploring freedom to screw your boyfriend all day long, which Buffy did do for a while.”