[1] The Trio summon a demon whose hallucinogenic venom makes Buffy believe that her implausible and nightmarish life as vampire slayer has actually been her own elaborate hallucination as a mental patient, catatonic in a hospital for the past six years.
Whedon added that the episode is intentionally left open to interpretation; the actual cause of the delusions, either the poison or Buffy's return to "reality", is not made explicitly clear.
"If the viewer wants," Whedon says, "the entire series takes place in the mind of a lunatic locked up somewhere in Los Angeles... and that crazy person is me."
[3] The website Women at Warp compares the "none of this is real" theme with the Star Trek: The Next Generation episode "Frame of Mind."
It's a powerful episode, and it's also a plot we've seen before on TNG, when Riker is held captive during a reconnaissance mission, and his captors act as doctors to make him believe that his experiences aboard The Enterprise were all in his mind.