Season 6 Episode 17
Episode aired march 12, 2002
after buffy is stung by a demon, she begins to have vivid day-dreams about a mental asylum. she gradually begins to believe that she is a crazy girl back in l.a and that sunnydale and all her friends are just a figment of her imagination.
at comiccon 2013, while speaking about this episode, joss whedon mentioned that, during his time writing astonishing x-men, he envisioned cyclops, 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.