well basically after intro stuff groups were formed. Some people went with Zim,Sniper, and Manchester into one of 3 doors. The groups worlds have not been revealed yet.

As for the other question the GM is not going to accept anyone else but the 4 person limit stands. However if you want to add another charactor after 4 you can simply write off the person you wish to drop. That will keep balance if some people decide to rp as another person somewhere along the line.