Halloween ep: Spike and Buffy dressed as a punk couple

In the fic I'm looking for, I think it was AU with Spike being human (not 100% sure).

Spike and Buffy dressed as punks and when the spell happened, I believe Buffy said her name was Liz (?) and Spike was Billy.

As I said, I'm not 100% sure as it was years ago that I read this :P

Thanks so much!

Something like that happens in Dancing in the Moonlight by Holly. Buffy dresses like slutty biker chick named Liz and William is a biker called Will when the Halloween spell happens.

http://dark-solace.org/elysian/viewstory.php?sid=49&warning=NC-17

A prophecy unfolds just as a new Slayer arrives in Sunnydale. A cocky, British, platinum blond Slayer with a devilish smile and a body to die for. And Buffy doesn't know what surprises her more—the fact that he's male, or the animal attraction that festers between them almost from the beginning

That;s it!
Thanks so much!