Find that user!
The process of finding a user is inevitably simple. But what if there's a twist? All players except one form the finders team to find out.
When the game begins, the one user should leave every room that he/she's currently in. Then, that user changes his/her username to something else, as well as changing his avatar to something that isn't that commonly used (to distinguish the user from the crowd). Lastly, that user joins some random room, and engages in conversation with the other users like you would normally. The finders team must find that user! If they managed to find the user, they must give a good reason as to why they think it's that user in particular. To make it kinda fair, the solo user must also pm one random person in the room that they haven't pm'd already every 3 or so minutes saying something like "I'm hiding from a mob. Shhhhhhh," as well as drop tiny little hints from time to time that they're hiding from other users in the chat. After some amount of time, the game ends. If the finders found the user, they win. If the user hasn't been found, that user reveals him/herself and the room they were in, and said user wins. Simple right?
Other Rules:
/whois and /w commands, or their aliases are unfair. You can't use them.
The solo user cannot join the Lobby. Believe me, he/she would be too hard to find.
This idea is terrible isn't it :c