Okay. So, I'm running Hall of Harsh Reflections sometime within the next week. (I've already started it, but the PCs have only gotten as far as Eligos.) Knowing the next event to happen (that is, one of the PCs getting replaced by a Doppleganger), I took one of the players aside, and asked him if he would mind playing a Doppleganger impersonating himself for a chunk of the adventure, and he agreed. The only problem with this (that is, a problem with the adventure) is that the meeting of the actual party member- that is, when the PCs (complete with Doppleganger) find the room with several doppleganger each impersonating the PCs. The way it is, how is a DM supposed to run that? Is he supposed to have the DopplePC immediately take over playing his actual tied-up self, thus alerting everyone in the party (out of game, anyway) that the member of their group is actually a doppleganger? To me, that sounded ridiculous. So instead, with the chosen player's cooperation, I'm going to have him continue to play the Doppleganger, and I'll play all of the people chained up. Hopefully, even if the players do immediately realize that they have a doppleganger among them, they won't know who it is.
But then, I had an idea.
You know what would be hilarious? You see, we started the adventure last week, and I took the player aside beforehand (in case we got to that point). We didn't, and we're left with a couple weeks before we play again, but I was planning on playing out a little scene with each of the players individually- one player is going to have the scene with the Rain Barrel man, the chosen one is going to have the scene where he gets kidnapped, and I haven't decided the other yet (as we have three players). Since these are going to be played out separately over the next week, none of the players are going to know what the others did until it's explain in-game. So I had this idea. Wouldn't it be hilarious if I decided to make another one of the players ALSO be impersonated by a Doppleganger? And the other? It of course wouldn't work with the current storyline, but wouldn't you think it was hilarious if you were a player in a campaign where every sngle character got replaced by a Doppleganger, but none of them (and none of their players) realized it? Just the thought of the looks on their faces when they all realize that their entire party isn't what they think it is makes me laugh.
Despite the fact that it could never happen, what would you all think if someone did that?
I'm also just starting to run HoHR, set in Eberron. In the conversion notes, Keith Baker suggests that the doppelgangers in this adventure be a separate group, unaffiliated with the criminal organization already established in the city of Sharn.
So I read your post and it got me thinking. What if one PC is kidnapped and replaced by a doppelganger from this group as established in the adventure. But another PC gets kidnapped and replaced by a doppelganger from the separate criminal organization, who want the PC to help them understand what the first group of doppelgangers is doing on their turf. ("See, there's this other group that has kidnapped your buddy Joe, and we want to know why. So we kidnapped you, ya see, and replaced you with one of our best spies, so they can keep an eye on the fake Joe. And we want you to come with us as we follow your friends, so when we confront them and go after fake-Joe, you can vouch for us, ya see...") Funny stuff.
My group just finished off Telakin. I got one player (the rogue) to buy-in early in the adventure and gave him a list of motivations and goals (which he did very well on). One of his goals was to have each of the other party members arrested at some point so that they could be swapped out with dopples. I played out the "betrayal at the bar" pretty close to the module and the rogue managed to talk the framed player (cleric of heironymous) into going along to jail quietly (nice to have a bunch of lawful characters!). For a change of pace, I didn't let the second player know that they had been swapped. Instead, I let the group get all the way to the mirrored room - with the undercover player leading - before telling the second player the truth. When the group saw their duplicates, I took each player out of the room individually and told him whether or not he was a doppleganger. We rolled initiative for actions, which at this point was just talking - each accusing the others of being dopplegangers while I played all the chained creatures. On the third round, I changed up and had everyone play the chained version of themselves. The next round, I had them switch back, EXCEPT for the cleric - he continued to play the "chained" version. His doppleganger had slipped out of the room on the pretext of "freaking out" to go raise the alarm. By this point, a couple of the dopplegangers had gotten free plus the true cleric, so no one was sure of anything. By the time the players started being confident of who was who, the rest of teh complex had been alerted and started coming in waves over the next few rounds. Turned into a heck of a fight and ended up with the real rogue dragging the corpse of his (fully-equiped) dopple and the rest of the party chasing the final dopple (the one impersonating the cleric and holding all her gear) into the maze, where they were promptly set upon by Telakin's guards and beaten to a pulp.
Lotsa fun.