On Everything2, in the chatterbox, the /invite command can be used to invite other users to a room you are in. This also works on User groups (like Gods and Editors), so they can organise cookie sales and trinket exchanges.
The command "/invite user" sends the user the message "Sender says Come join me in room." in their Message Inbox. selecting room moves the invited user to that room.
Example: if i was in Political Asylum and wanted to discuss gun ownership with fondue, i'd type /invite fondue
fondue would see in his message inbox:
gnarl says Come join me in Political Asylum.