...and I developed a curious wondering. In my stash of Buffy-fic, a large number of them revolve around the Halloween episode with Janus and their costume choices.

As you can imagine, by simply substituting the Scooby Gang's various choices, you open entire universes of different plots. Looking at my saved fic, it seems I'm partial to the one's where Xander becomes Superman or Ironman. I remember there being a really good Xander as Freddy Kreuger one that I never saved because horror isn't really my thang.

So back to my wondering. My question is this, can you think of any other genre episodes that have basically spawned such a variety of fanfics...? Off the top of my head, I can only think of the Mirror Universe style fics but they're kind of a cheat! :p