"Asylum Buffy" is a name to describe Buffy, as she is stuck inside an alternate world that has placed her into a mental hospital.
In the season 6 episode 'Normal Again' Buffy is stabbed by a skewer from a demon summoned by the Geek Trio. The injected venom gives her recurring visions of being a patient in a mental hospital with her being the Slayer just a delusion.
Asylum Buffy world
Asylum Buffy is portrayed as having been an inmate in a mental asylum for the previous six years when she was diagnosed with a form of schizophrenia. Her mother Joyce is still alive and still married to her father Hank whilst her time in heaven after her death at the end of season 5 is explained as her having a temporary recovery from her condition the previous summer. The doctor theorizes that Dawn's sudden creation was the result of Buffy needing a familial bond after Joyce's 'death' within her delusion but that the fantasy world Buffy has created is now no longer as satisfying to her as it once was, hence the inadequacy of the Geek Trio compared to previous villains and her visions of the 'reality' of the asylum. Joyce pleads with Buffy to accept the reality of the asylum and reject the fantasy of Sunnydale but in the end Asylum Buffy chooses the tougher path of bearing the burden of being the Slayer, lapsing back into a catatonic state much to her parents distress. The final image of Asylum Buffy is of the door of the mental hospital slamming shut on her room.
At ComicCon 2013, while speaking about this episode, series creator Joss Whedon mentioned that during his time writing Astonishing X-Men, he envisioned Cyclops, a Marvel Comics mutant character whose real name is Scott Summers, making a reference to a female cousin of his who had been sent to a mental institution for believing she was a demon hunter. However he could not find an appropriate place in the storyline to fit it in and therefore it was never featured. Had it occurred, a convincing argument could have been made that the events of "Normal Again" take place inside the Marvel Universe, and that the events of both the Buffy and Angel television series take place entirely inside a Marvel mutant's cousin's mind. However this premise faces the difficulty that the X-Men are fictional characters within the Buffyverse, referred to as such by both Andrew and Xander. An alternative suggestion is that the X-Men and Buffy the Vampire Slayer take place in the same reality, the X-Men's real life exploits recorded in comic book form and Cyclops' remark concerning his cousin referring to Buffy's short period in a mental institution between the events of the Buffy movie and her relocation to Sunnydale at the beginning of the television series.
In 2011, Sarah Michelle Gellar guest starred on her former soap opera All My Children, one of several past cast members to return to the show in the final few episodes in order to commemorate its conclusion after 40 years. Gellar played a young woman who had been brought in for psychiatric evaluation, as she claimed to see vampires. This could be interpreted either as the actual Buffy the Vampire Slayer, who has been percieved as mad simply for pointing out real vampires, or former Asylum Buffy (judging by her fashionable clothes/appearance and coherent behavior) undergoing recuperative treatment after suffering a slight relapse.
Ramifications of Asylum Buffy storyline
In his DVD commentary for the episode director Rick Rosenthal comments that the ending is ambiguous and leaving it to the viewer to decide whether it was real or not. In interview Joss Whedon, commented that it was the "ultimate postmodern look at the concept of a writer writing a show," explaining away inconsistencies and unreal elements of the show "the way any normal person would." He added "If the viewer wants, the entire series takes place in the mind of a lunatic locked up somewhere in Los Angeles... and that crazy person is me. Although, personally, I think it really happened."
Fan theories exploring the implications of the episode and his statement are referred to as the Normal Again alternative, exploring the possibility that Buffy being the Slayer is simply a 7 year long delusion beginning when she hallucinates first meeting Merrick and ending with the final scene of Chosen, which actually represents her regaining her sanity once more. It is noted that by the end of the final episode Buffy has destroyed Sunnydale, literally overcome her demons and triumphed over herself in the form of the First Evil. What is more the final words in the series are Faith telling Buffy that she now has to 'live like a regular person', and Dawn asking 'what are we going to do now?'.
However, there are several logical difficulties with this interpretation presented by the narrative. Events occur in the Buffyverse without Buffy ever being aware of them, notably never learning the truth about Xander's lie concerning Willow's message in 'Bargaining pt2' and virtually the whole of the Angel episode 'I Will Remember You'. By contrast, Asylum Buffy is present in every single scene in the mental hospital, as she would be if the asylum wasn't real and was simply her delusion. Sunnydale Buffy is also aware of current events, which would be impossible if she were in a catatonic state in an asylum, whilst on several occasions, Sunnydale Buffy attempts to walk away from her calling as the Slayer (which is illogical if it is her escapist fantasy). An alternative suggestion is that Asylum Buffy is real in a parallel dimension, but regains her sanity at the end of 'Chosen', as Sunnydale Buffy no longer bears the strain of being the lone Slayer, and Asylum Buffy is no longer tortured by the resulting visions from her.