Inception: Chased around the globe by anonymous corporations and police forces, the way the projections persecute the dreamer? Admit it: you don't believe in one reality anymore.
Buffy: Cause what's more real? A sick girl in an institution, or some kind of supergirl, chosen to fight demons and save the world? That's ridiculous. A girl who sleeps with the vampire she hates?!? Yeah, that makes sense.
This serves two purposes, first to advance the plot of questioning whether the protagonist is dreaming and second to give a wink to the audience at the artificiality of what they are watching.
Basically my point is that Buffy already did it Inception! Buffy even had to face the decision of killing her (subconscious) friends so she can wake up. In similar Inception fashion, the episode ends ambiguously, leaving open the possibility that the entire show is just some St. Elsewhere delusion. Give her the kick Willow!
