Adding players to a game as NPCs only - legit?
Say for instance that I wanted to add some lurkers to a game, but in order to be fair and kosher to the players I wanted to have them listed on the cast list so that the other players are aware that other people are present and watching what they say (which I'm aware would mean actually adding them to the game as players and not just Lurkers, but they wouldn't be actually playing so I'm calling them lurkers for the purposes of this question), and I decided to tag those people as 'Lurker 1', or 'Watcher 1' or 'Twinkletoes 47' or whatever so that it was clear that they weren't playing characters.
Ideally, I'd want to give those 'Watcher' characters NPC status, so that they appear unobtrusively down on the NPC cast list instead of cluttering up the main cast list with non-characters.
Are there any rules against doing that? I've seen players that abandoned a game and/or went on hiatus moved down to NPC status before (while still having control of their character), but I'm not sure I've ever seen players added with only NPC status.