No More Fakes is a shared story universe, that was started on the Transformation Stories Archive discussion list back in December. It was extremely popular for a couple of months; then it sort of died off, though it seems to be having a slight resurgence lately.
Here's a brief synopsis of the series, written by Arthur Pearson, as it appears in Brian Eirik Coe's TSA FAQ.
In The City (a specific city that is deliberately not named), Don Keyhoe, dressed up as a wizard, got out of his car on his way to the Raucous Chicken Club, a mansion or converted mansion. It is Oct. 31, 1996, and the club is hosting a Halloween costume party. Aculcar of The Orange Stripe, an actual wizard of considerable power, appeared nearby on his way to see a man about an amulet. Don made a practice faux magical gesture in preparation for going into the party, and Aculcar recognized it as the secret wizard hand signal for "Follow me to the Treasury." Aculcar followed Don into the Raucous Chicken, and repeatedly asked him about the amulet. Don came to the party to pick up chicks, so he ignored Aculcar again and again. He eventually made a flippant comment to the frustrated wizard, who finally probed Don's mind for the truth. Upon finding himself at a place where everyone was not who they seemed, he cried, "I've had it with this roomful of FAKES!" and disappeared in a puff of smoke. Everyone at the party was transformed into what they were costumed as, gaining some of the abilities and at times the mindset of that form.
The police arrive and try to get control of things outside the club that night. Eventually during the night after things calm down, they enter the club. Ambulances and firetrucks show up during the night, some injured transformees are carted off to the hospital. The X-files exist in this world (although I personally entertain the idea that two who came as Fox & Scully were at the party, left the party, and forgot ever being at the party. The police go along with them in the X-Files story just because they'd be experts in this sort of investigation.) and arrived late night Oct 31/ early morning Nov.1, and began interviewing people. At some point a team of psychologists are called in to help with mentally changed transformees, and are part of an unofficial line of people to see if you're a transformee and you go to the police or hospital. The press grab hold of the story and fly with it that night. (although there seemed to be no press presence at the club in any of the stories...) Eventually, reports on transgender, animal, superhero, and toy transformations are shown. Nov 2, a scientist claims that the transformations make one unaging. Nov 3, unknown to most everyone, the powerful sexy wizard Caltherana (even more powerful than Alculcar) arrives on earth, summoned by some wizards. She is staying with a college kid turned wizard. She will not reveal her nature to others unless they ask it, and will... consider it, if asked to be changed back. Note: NO one can find anyone who can overturn the rules she will enforce. Nov 4 - by this time, someone has proposed another party at the Raucous Chicken on the 14th, hoping lightning will strike twice.