No, I don't have any existing examples, sorry.
Actually, where I got the idea from is kind of a long story. Er...literally.
We used to do an activity in my writing group where we'd split into teams of four or five, and everybody would start a story. Then the timer would go off after five minutes and we'd each pass our story to the person next to us. They'd continue it for five more minutes, then pass it to the person next to
them, and we'd eventually each wind up with a story with parts written by everybody else. (Sort of like the three word story that's going on now, only slightly more coherent...)
At some point a couple of friends and I got so addicted to these that we started running them over e-mail, and they eventually took on more roleplaying aspects with one person pitching a setting (an archealogy dig and an Egyptian curse, space pirates and an alien war, even a demonic toy factory; they pretty much ran the gamut) and everyone writing a few character bios to complement it before the story actually began. (In this case the "mod" would also play, and would do something to nudge the story along if it ever fell into a rut.) There were also a few assigned roles, where the story needed a few specific characters right off the back, and the mod would describe what they were like and ask for volunteers to play them.
It just crossed my mind because I remember one of them actually involved a werewolf, a vampire, a masquerade party, and a bunch of rich, snooty people who deserved to die.
Of course the similarities pretty much ended there; I think the inspiration for it was actually the game Clue, and by the end of the story the humans had killed more people than the monsters did. And everybody knew the vampire was a vampire (she wore a scarf, had pale skin, and "NO GARLIC!" became something of a catch phrase) only most of the characters were to dense to figure it out, and the werewolf was actually a good guy who was subject to excessive body hair and violent personally changes whenever he was exposed to moonlight. (Luckily it turned out munching on a vampire was the cure for lycanthropy...)
The whole thing was pretty ridiculous, but fun. We'd wind up with situations like: "Oh dear," Samantha sniffs. "Reginold has gotten his entrails all over my chandelier. How inconsiderate! Benjamin, do have the maid come and clean it up." or (to paraphrase): 'Bridget comes back into the room, looking relieved. "Oh, what a weight off my shoulders! I've been so worried, what with the electricity going out and the murderer on the loose that I decided to call my lawyer and have him write out my will. Markus and Maximillian, should anything happen to me tonight I want you to know that I've left my mansion in Florida and my entire collection of diamonds to be split between the two of you." (Bridget and Maximillian later ended up dying under not so mysterious circumstances...)
LOL, wish I'd kept a copy of the e-mails now, but that was a few years ago and the e-mail acocount I used then is long gone...
