Let me 'splain. No. Take too long. Let me sum up. (<--10 points, people - I know you can do it.)
Every 3-4 months a forum member's MC hosts a party in the setting of their WiP. Invitations are sent out (via a thread to "everyone"). Your characters jumps in with their response and then, on a specified date, the fun begins. The most recent party was held in 1493 Constantinople. Our lovely host for this round was Rosa, aka Deniz.
The host gives setting details and description, and informs everyone what will be taking place during the party. (Parties last anywhere from a long weekend to a week.) Everyone brings their characters and dives in. We play with one another's characters and have a good old time. We don't worry about typos and writing mechanics - we just go for it, and nobody judges. I'm amazed at how well we are getting to know the huge cast of characters - there are times where I have to go back and read a post because I can't believe it's not the actual author writing them.
Oh, and chaos and mayhem reign. We've had, bombings at the London Blitz, blizzards while skiing in New Zealand, an alternate universe with ghosts from the Civil War in Cherry Hill, and so much more! At night, there's usually a break from the mayhem and a few trips to the [cough*
Some of the party-goers include: FBI agent, rock stars, soldiers, vampires, magikers, King Charles II and some of his court, a talking cat with a time traveling boy, a married threesome (m/f/m), a silky/selkie, paranormal modern day/ancient Egyptian travellers, werewolves, a widowed, retired teacher her adopted daughter, and Marine *friend*. Phew. No wonder mayhem ensues!
If you have a group of writers you are close with (crit group, friends, or website you frequent) I can't recommend something like this enough. It's so much fun. Oh, our last party = 172,000+ words!
In case you're wondering, it's not all about fun. Most of us go in with a goal (from a specific time in our characters development) that we are trying to reach/figure out. It's unbelievable what you can dredge out of a character when they aren't forced to stay in their own setting. We have side threads for commentary and after threads discussing what we got out of it.
Okay, this was not a summary, most definitely an explanation. Sorry, I tried.