Sorry people, but I'm going to annoy you with another fic search ^^;;;
I've been searching for this particular fic for days now, and I still can't remember where I first found it >_<
Anyway, here is the deal: it was a spander fic (no kidding XD), where the scoobies became actor and accepted Joss Whedon's offer of doing a TV Show based on their years at Sunnydale as Vampire/Demon Hunters.
I remember that at some point, Willow had refused that Joss hired an actor to play Tara so the writers had decided that in this case, they didn't need a Tara. Still, they wanted a gay relationship, and asked Spike and Xander if they would accept to play the part.
If it rings any bell, let me know, please! ^__^