So i have an idea for a dnd session and id like to hear your thoughts, a player character gets captured by a doppleganger, and the charector who played the player chaector now plays the doppleganger pretending to be the player charector, is this idea good?

I’ve heard of that before. In that instance the players never discovered the switch and died during an opportune moment of betrayal.

i think it would be interesting, but you need to at least communicate with the player you want to switch to see if they are cool with playing an evil doppelgänger of themselves. And try to work in things to at least give the other players a chance to figure it out.

I've done that once, but it was resolved the same session the switch happened. 

I also didn't tell my player it was a switch, instead, I told him it was some sort of charm effect. I knew my player would play along though, especially since it was for a few hours at most. 

When the party encountered the boss, I had him go full betrayal. They killed him, and after searching the place, they found the original character, and that's when it was revealed to have been a switch. 

I think it was a fun experience to everyone because it was unexpected, but also because it was short, both IRL (half a session at most), and in-game (half a day). The player also enjoyed having a peek behind the screen, and sharing a secret with the DM. 

I saw this once. The DM conferred with the player beforehand and the player agreed. (It's all about the communication.) The player dropped subtle hints for the rest of the campaign, nothing overt that would outright disrupt things but still managing to hinder the group's progress occasionally. There were other things like avoiding silver or staying outside of a detection range or being a pyromaniac (which was already part of the original character's design before the switch) and setting small fires that would go out of control and destroy places that might have had more clues, all things that he passed off so smoothly that nobody took notice until the big reveal during the boss battle. Then, the group thought back through their adventure and realized all the tiny things they had missed throughout the campaign - a whole lot of tiny things, all done by the player on his own once he and the DM agreed on the switch.

Of course, the DM knew the player would be totally into it. So, you'll need to have some idea beforehand if you can go that route or if you need some other option.

I'll say that this idea depends greatly on your group, this kind of hints is likely to be missed by a lot of people simply by virtue of trusting other players. 

I know my group would have missed it, even though they might have enjoyed the reveal. It would have needed some big clues, such as openly refusing to handle silver coins, for them to notice. 

I am currently finishing up a campaign where this happened at one point. My main character is a Warforged Horizon Walker Ranger, but to introduce them in the first session, the DM needed me to have a different character to play at the start. So I rolled up a Changeling Glamour Bard. After that first session, the changeling has appeared a few times as a DM character (in disguise) to help out the party with small stuff.

In this campaign, we actually have two characters each, the main good party character, and a side evil character. At the end for the BBEG, we each played both of our characters. The mission giver for the good guys, wanting to stack the deck against possible betrayal, temporarily banished my evil character (Half-Drow Warlock) and replaced them with the changeling.

We are going though the BBEG dungeon and the other evil characters are "hey, since when can the warlock inspire?" and "why isn't he using eldritch blast?"

Once the BBEG was dealt with, the evil party gets teleported out (with the warlock rejoining them at this point). The first thing that happened was "Everyone, grab the warlock". RP interrogation ensued, and now some of them are very curious as to what happened.

Thank you for the help. My main worry with this is the part members will never trust each-other ever again because anyone could be a doppleganger, would this be a problem?

That is a fair point, but in the group that I saw, they (rightly) figured it was something that would be enjoyable only once and weren't paranoid about it. This is partly because they knew the DM well enough.

I guess, in the end, only you could really answer that question. 🤷‍♂️

Quote from MrShaardvark >>

Thank you for the help. My main worry with this is the part members will never trust each-other ever again because anyone could be a doppleganger, would this be a problem?

 

I was recruited/murdered by a Doppleganger and then I proceeded to wipe out half the party.  I can't say I didn't enjoy it.

But, my experience post that, was that everything went back to normal because of two things.  1st, the party's makeup didn't contain evil characters, and 2nd the DM only did this once.  So it became a once off experience, that everyone wrote off as an interesting diversion.

I could certainly see it with some other groups it and it going poorly; especially ones with trust issues up front.  Those groups had a hard time getting things done, while their backs were looking for walls constantly.

Thank you for the help