There are situation in roleplaying game sessions when players are totally powerless because their characters are unable to act because they are incapacitated, separated from the group or in any other situation where the player is doomed to sit at the table unable to play. That’s a situation that in my humble opinion should be avoided at all cost. From my own experience I can recall at least two situations where my characters where unable to act for the majority of the session, so I was doomed to sit there and watch the others play. And I can tell you that it was no fun.
One of these situations occured in a game of “Vampire – The Masquerade”, where my character got caught by several ghouls of an enemy vampire. During a short struggle my character was incapacitated and I was in “torpor”. It took my fellow party members a whole gaming session to rescue my character, while I watched from the sidelines. That was some wasted Saturday afternoon, I can tell you. So, what can a GM to avoid something like this?
The easiest method is to ask the player in question not to show up for that session since it is unlikely that his character will be back on his feet during that session. That is of course not possible in any situation, since there could be some hope that the rescue (or recovery) is getting faster than expected, or when the event that took the player’s control over his character away happened at the beginning of a session.
Another way to occupy the player is to let him play one of the NPCs. In a lot of campaigns I have played in, there are usually a lot of NPCs that are friends, colleagues or acquaintances of the player characters that can be used as a replacement character until the original character is back in action. Or, if time permits, let the player create a new character that he can play until the situation is solved. Everything is better than let someone sit at the table with no task at all.
Some games recommend creating several characters for each players. Especially in games like “Call of Cthulhu” or “Chill”, where player character death or insanity is more or less common, it is advisable always to have some replacement handy. But this should always be the last resort in my opinion. In a roleplaying game everyone should have fun. And being in a totally powerless situation (as a player) or having to play a NPC is not my idea of fun, so the GM should try to avoid such situations from the start especially if only some fumbled die roll doomed the player to become a spectator for the rest of the evening.