I guess most of us have had this happen many times over the years. You are in an ongoing campaign with a stable group of players, when a friend or a friend of one of the players, or someone who has moved away visits and asks if they can play. Of course, you say yes and if you have a handy NPC nearby, give them control of them, or if you have a bit of notice, allow them to roll up a character who will make a cameo in the campaign.

It nearly always changes the tone of the game, for that one or two sessions, whether an NPC starts acting slightly differently because he is now in the charge of a player or a new character changes the group dynamic, brings new ideas etc. Sometimes this is a great shot in the arm for the game and especially if it's a friend you haven't seen for a while, is a great social time. But sometimes it derails the game.

So my question is this. What are the best ways to mitigate this temporary change in tone? Is it even desirable? Any tips on how you've handled this in the past?

(As an aside, i had an awesome one-off session with a visiting friend a few years ago. He flew down for the weekend and joined our game that week. I handed him a character i had made who was going to make an appearance that week as a guide for the PCs. I hadn't come up with a name by the time he arrived, so i said "Name him as you will." Fast forward a couple of hours to when he met the party and they say "what's your name friend?" To which his reply was "Asuill" )

We frequently get "guest" players, as we have a few cats who'd like to game with us on a regular basis, but their schedules prevent them from being regulars. In our SR game it's very easy to integrate them as the PC's are playing under cover law enforcement agents on a task force. So adding or subtracting characters is easy.

In our upcoming D&D game I am not sure how it will work.

I don't think there is one way to deal with this, really. I've had guests show up, and been really sad to see them go at the end of the night, but I've also had at least one that forced me to brng the session to an early close because he seemed hell bent on trashing the game.
interesting topic, Dan.

edit: I would, however, suggest keeping an escape hatch on hand- in case you have to shut things down early. Suggestions: DVDs, booze, "emergency" phone call, ect...

Quote from: Serious PaulIn our upcoming D&D game I am not sure how it will work.

I'd love to see how you handle it for D&D...in person...in..like...a week and a half...when I'm in Holland...hint...hint...

Quote from: James J SkachI'd love to see how you handle it for D&D...in person...in..like...a week and a half...when I'm in Holland...hint...hint...

The real question will be if we're running the D&D game by then. Two players are gone to Burning Man, another is getting married and taking two weeks in Mexico, and while that still leaves me with four solid players I want to wait until the burning man crew is back-in part becuase one is a new player who really asked us to get the game going.

But yeah dude keep me in the loop, and we'll definitely have some game days coming up! This week is Thursday. (Shadowrun I think. Maybe Star Wars SE)

It depends really - I've given guest's characters when regular players aren't available and haven't had problems. If that's not an option I've usually a couple of npcs I can fit in with notice.

Otherwise I let them take on roles when they can take on npcs the party encounters. It makes a change for the characters to have someone else's interpretation and easier to introduce multiple npc encounters.

No horror stories, but maybe I've just been lucky.

I haven't tested it yet, but my theory is that if the NPC is described a la "The Seven Sentence NPC" from Dragon #184, the guest player will have a pretty sound idea of what the character's like, and play him/her more accordingly.

Basically, the article suggested writing a descriptive sentence for each of these:

   1. Occupation & History
   2. Physical Description
   3. Attributes & Skills (above & below average, class & levels)
   4. Values & Motivations
   5. Interactions with Others (how does the NPC act toward others in general)
   6. Useful knowledge
   7. Distinguishing Feature

In theory, it seems like this should allow any NPC to be picked up by anyone at the table and played reasonably according to what you intended, while still allowing room for individual quirks.  In theory.

Quote from: One Horse TownSo my question is this. What are the best ways to mitigate this temporary change in tone? Is it even desirable? Any tips on how you've handled this in the past?

An NPC is always my first option, and we don't mind the possible changes in tone. Good ideas are followers of the PCs, allies and similar.
 
If that's not possible or convenient, I usually hand him a pregen, or guide him to make a quick PC, letting him know which traits or skills would be more useful.
 
If everything fails, I let him guide any NPC, including making rolls for them in combat and so on. That way, he acts like a co-GM.