In writing, breaking the fourth wall happens when the author inserts themselves into their writing. As an RP, the Breaking the 4th Wall thread is a room where both characters AND their authors can pop in and out at will and interact with each other, other authors, and other authors' characters.
This thread isn't intended to have a structured plot. It's open to all genres. Multiple character/author interactions can be going on at the same time, moving at their own pace.
Note: this is an RP that I liked from the NaNoWriMo site and I am copying the general idea of.
I just reread the FAQ (it changed since I looked at it last!) and what I have in mind seems to qualify more as a "free world" RP than anything else. So, a free-world, sandbox-type thread that allows characters and their authors to interact with each other side-by-side. Sounds like great tiemz, yesh?
The setting: a room with a lit fireplace, squashy armchairs/sofas, and a (full) attached kitchen and a well-stocked bar. The minor details of the room change as needed depending on what's going on. Authors have some degree of "authorial" powers over the setting. (In the past that's mostly meant spontaneously-appearing food plus there was a floating picnic at one point.)
Uh... And there's probably more but it's past my bedtime so I'm logging out now.