This was the third Buffy game I had done using roughly the same characters.  I had originally created the series concept (Fifties Slayer reincarnated in modern-day Santa Cruz) and characters as my test drive of the Buffy system.  Since then, I've run three convention games using them.  I think it's a good device but it is a little silly, which I generally try to play to. 

My preparations were described at Prepping for Buffy at ConQuest

An overview of the series and character sheets can be found at The Slayerbot Series

Explaining my plans in advance, this event was focused on character relationships with a wrapper plot to bring those out.  The central device was that the Slayer, Barb, was split into two bodies -- these were the fifties Barb who only knew her early life, and the modern Barb who only remembered since her reincarnation.  Also, fifties Barb was straight and modern Barb was closeted gay.  After that concept, I knew I wanted a villain from the fifties who created a duplicate Barb body.  I settled on making "Dr. Botnik" -- an over-the-top crackpot beatnik who builds robots.  I also came up with a guest star -- a male romantic interest for Barb from the fifties. 

I got seven players for the event.  One player (Julie) signed up but walked out prior to the game start.  For the others, I had a mix of six fairly typical twenty-to-thirty-something gamer guys and a teenage girl.  What I got was:

• Paul took "modern" Barb.  He had some misunderstandings about the facts of the background at first, but after a slow startup period he was pretty good as the modern Barb.  The relationships with the girls didn't take hold, but he had great interactions with fifties Barb.
• Fifties Barb was played by (I think) Jesse.  He was a bit over-the-top but still serious in this one, playing a relatively submissive and proper girl.  A interesting take was that in the written backgrounds I had defined Barb and Steve as having unexpressed romantic tensions.  However, Erik as Steve announced himself as Barb's boyfriend and Jesse went along with it.
• Steve Brant, the mystical bad boy from the fifties was played by (I think) Erik.  Steve and Fifties Barb were an amusing critique of a dysfunctional sexist relationoship.
• Autumn played Tori -- the dangerous, promiscuous, vampire-hating goth chick who was secretly in love with Barb.  She worked pretty well, I think, playing out a hatred of Steve.
• Jerry, who had played in both of my prior Slayerbot games, played Johnny the fourteen-year-old inventor.  He was pretty comfortable with his niche as tech master.  He had his moments in the spotlight and enjoyed himself, but didn't play a central role in the story.
• Jon -- who had played in my Dogs in the Vineyard game -- played Ashley, the "Gay Vegetarian Wiccan Rich Girl".  He said that he had trouble with the character.  Her main relationshops were as ex-girlfriend of Tori -- which Jon felt uncomfortable playing since Autumn was a teenage girl -- and with Owen, whose player also wasn't very comfortable.
• Owen the "Popular Surfer Dude" was played by (I believe) Simon.  He had trouble with the character.  He initially latched onto "The Dude" being the protagonist from The Big Lebowski.  I emphasized the differences, but that was still the center of vision, I think.  In retrospect, this was a serious problem since the characters were almost opposites.  Lebowski was a sluggish older detective whereas this character was an athletic but clueless teenage hunk.  He never used his popularity or athletics, and at some point attempted to use his Notice skill and was surprised.

The plot went pretty well.  By design, the external plot per se was not the point.  There was some good use of the "Plot Twist" mechanic by several players, including Jon who spent that Ashley knew a real psychic who could diagnose what happened to Barb's soul.  The logic was simple, and the PCs were able to proceed reasonably.  Notable bits:  they initially called Dr. Botnik by cell phone, and while ranting against him, Fifties Barb said:

Barb: ...while you go ahead and make your army of robot vampires or whatever.
Botnik: Hold the phone.  Say that again.
Barb: What?  Army of robot vampires?
Botnik: I've got to take that down.  It's happening... visionary, even.

One of the players commented positively that "It's in the tradition of early Buffy to have a villain that's totally non-threatening." -- which was certainly my point.  The central conflicts were within the party and within the PCs. 

As I predicted, only a few relationships actually panned out.  Fifties Barb and Steve had a simple but amusing dysfunctional relationship.  The two Barbs had excellent clashes.  And Tori and Steve had a good hatred/rivalry.  The others didn't really pan out, but I set up a lot of relationships with exactly the view that few would work out.