Playing an NPC

One of the cool things about being involved in as many gamer circles as I am is that I get to occasionally drop in on someone’s game and play a single session or three, usually as a fill-in. I get invited a fair bit, but I only ever make it out to a few games, as my schedule is usually pretty ridiculous.
Being a drop-in character in a long-running campaign is different from playing a character from the beginning, or joining full-time. You aren’t there to play a character, really – at least not in the traditional sense. You’re there to fill a gap, or to make something happen, or sometimes both. In a lot of ways, you are a glorified NPC, an extension of the Game Master’s will. There are almost always plans for you.
So when I come into a situation where I might be filling in a gap, the first thing I do is put my Game Master hat on. I come up with some ideas about who or what the character I’ll be playing is, and how that is going to work into the overarching plot of the game. Sometimes that’s as simple as “My players need a healer for a few sessions while Jenny’s moving into her new place,” sometimes it’s as complicated as “I need someone who is not me to steer the group in a political direction that is better suited to the complete dissolution of the current regime in favor of one that is strongly detrimental to the player characters.” I treat the former like I’m a player. I treat the latter like a special sort of Game Mastering in Miniature.
One of the biggest benefits to this, I find, is that a fellow Game Master brings something new to the table, a perspective you don’t have. In my case, I bring a lot of plot. No character I create lacks a backstory. No character I create lacks goals or aspirations, and that can often change the dynamic of the table drastically. When my goals and the goals of the other player characters don’t exactly match up, all the better for the dramatic tension it causes. Then, when things hit a peak, I leave and let the Game Master figure out what happens next.
Where this helps other game masters is in the flexibility it offers. If one of the players sitting at your table is pulling the party towards a specific direction, the rest of the players aren’t going to jump down the Game Master’s throat for rail-roading. A lot of times, I’ve come up with the direction entirely on my own, or with minimal direction from the Game Master, which gives me a lot of flexibility in how I get that plot point to work. It also means that I can surprise the Game Master with a point of view he or she hasn’t considered previously, a plot point that might not work in any situation except as initiated by a player-character, or a situation that is much more dramatic because of the tension that comes from interacting with another person playing a single character.
It can also be a lot of fun, plotting and planning things that the other players may or may not expect. I’m looking forward to sitting in on a few sessions of Siobhan’s Changeling game, for instance, mostly because I don’t think anyone has any clue what it is they’re dealing with, and it has the potential to change the political landscape of the game forever.