Cordelia makes a slightly different wish from Anya, and ends up in a very different Sunnydale. Cue Scooby Gang consisting of Buffy, Faith, Willow, Xander and Jesse. Not forgetting their adult advisors Giles, Jenny Calender and Gwedolene Post. Superb use of characterisation and continiuity, and just plain fun in everyone's interactions with each other. You really get the feeling of a tight-knit group, relaxed and used to each other.
Go. Read it.
And now a meme.
I'm fairly sure the stalker one's meant to be nothing at the end. :D