I would honestly play an entire game with the tighter narrative focus of Chateau Irenicus. I recently played BG2 after my longest-ever time away from the game (4 whole years!) and for whatever reason, I noticed the dialogue in the first dungeon a lot more. Because the game *knows* that your only options are Minsc, Jaheira, Imoen, and Yoshimo, all of the dialogue is actually calibrated to have 3+ participants, and they have honest-to-god conversations together instead of mostly one-off banter exchanges or interruptions.
Imoen's trauma particularly stood out to me and it really sank in how demented Irenicus was as she reacts to all of his different rooms. Making you explore and escape the main villain's dungeon (which is dripping with his memorabilia, evil deeds, and shattered psyche) was such a neat way to introduce him.
Oh, speaking of: you're doing a David Warner voice right? Right??
The only other place they show up is in the first god trial in Throne of Bhaal if you're Good, which always puzzled me as a player because I had no idea why all these doppelgangers were showcased in a boss rush. I never played BGI until two years ago, so on every other playthrough I was so confused. Was it just because of that one dude in Irenicus's dungeon? Weird.I don't think we even see any doppelgangers the rest of the entire game.