Note that extras tied to specific episodes are reviewed with those episodes.
Hush Featurette briefly covered the making of "Hush." It contains interviews with Joss Whedon, Jane Espenson, Christophe Beck, James Marsters, Nicholas Brendon, Douglas Petrie, David Fury, and Loni Peristere. Whedon talked about class issues in the upper-class Gentlemen and the lower-class footmen. Peristere discussed the floating Gentlemen effect. There are no spoilers past "Hush."
The Sets of Sunnydale Featurette discusses the new sets needed for the fourth season. It includes interviews with Jane Espenson, Joss Whedon, Nicholas Brendon, James A. Contner, Carey Meyer, Douglas Petrie, David Fury, and Marti Noxon. We learn that the initiative set was at a real government installation. The UC Sunnydale hallway was simply the Sunnydale High hallway redecorated and inspired by real hallways at UCLA. There are mild spoilers through the end of the season and a shot of a storefront that will play a significant role in season five.
Spike, Me Featurette mostly involved James Marsters talking about his character. It includes interviews with Marsters, Joss Whedon, Jane Espenson, and David Fury. Marsters talked about how his character was initially designed to be a disposable villain who would get out of the way. He also theorized that Spike abused Harmony as misguided vengeance for Drusilla dumping him. He said that he always played Spike as being attracted to Buffy, even when Spike was with Drusilla. The decision to make him a regular character was made during the filming of "Lover's Walk." He was intended to fill Cordelia's role of someone who will be blunt with Buffy, but Anya took that role. Part of the interest from this featurette is hearing James Marsters speak with his natural American accent. There are major spoilers through the first third of the fifth season.
Buffy, Inside the Music Featurette covers the scores from different episodes. It includes interviews with Marti Noxon, Christophe Beck, Joss Whedon, Douglas Petrie, Jane Espenson, John King, and Parry Gripp and Steve Sherlock from Nerf Herder. Beck discussed the process he used to create a score for the show. Much of the focus was on "Hush," but Beck also discussed "A New Man," and "Superstar" and King discussed Giles's singing and the use of bands in the Bronze, including Veruca's band. The two Nerf Herder members discussed the creation of the Buffy theme music. There are spoilers through the end of the season.
Oz Revelations: A Full Moon Featurette covered the character of Oz. It included interviews with Joss Whedon, Seth Green, Marti Noxon, John Vulich, and Douglas Petrie. Whedon talked about how Oz was based on a real person he knew and how he wanted to draw the plot of Wild at Heart over the entire season. Green talked about how he auditioned wearing thick rimmed glasses and how he wanted to go back to being a recurring character because he felt that Oz was pushed into plots where it did not make sense for him to be. Vulich discussed the evolution of the werewolf costume. Most of the clips came from the second and third seasons. There are major spoilers through episode 19 of the fourth season.
Cast Biographies describes other acting and writing credits for Joss Whedon, Sarah Michelle Gellar, Alyson Hannigan, Nicholas Brendon, Kristine Sutherland, Anthony Stewart Head, James Marsters, Marc Blucas, Amber Benson, and Emma Caulfield and includes brief personality descriptions for the characters they play on Buffy. The focus on the personality of the Buffy characters rather than what they did eliminated most spoilers beyond the fourth season other than whether the character might appear in the fifth season.
Season 4 Overview summarized the fourth season of the show. The focus was on the episodes and discussed "The Freshman," "The Harsh Light of Day," "Wild at Heart," "The Initiative," "Pangs," "Something Blue," "A New Man," "The I in Team," "Goodbye, Iowa," "This Year's Girl," "Who Are You," "Superstar," "New Moon Rising," "The Yoko Factor," "Primeval," and "Restless." It featured interviews with Joss Whedon, Marti Noxon, Douglas Petrie, Anthony Stewart Head, Jane Espenson, Seth Green, Tracey Forbes, David Fury, Amber Benson, Danny Strong, James A. Contner, and Loni Peristere. Joss Whedon talked about how the main theme was on the life changes that occur when people go to college, although Doug Petrie saw the theme as science vs. magic. Seth Green talked about having fun with crew members' discomfort with his nudity. Doug Petrie talked about how the writers were split on the Angel vs. Riley fight in "The Yoko Factor." Most of what they talked about was stuff we could figure out from watching the episodes. There were spoilers through the end of the season.
Still Gallery is a series of 57 stills from the show. Most are of the regular characters, although characters like Parker, Faith, Angel, and Tara appear alongside regular characters in three or four stills each.