I don't know if this is exactly the sort of thing you're looking for, but your question puts me in mind of a tabletop game I was in long ago. It was a Vampire: The Masquerade game, all female (and yes, we did get some odd looks the time we played in the game room of the local comic shop), and the game started with all of us as humans -- the first couple of sessions were playing out our last days as mere mortals.
One of those early sessions was at the ST's house, and the characters stumbled into an old house where a magic ritual of some kind was happening, a ritual that made us relive the deaths of a group of people who had been killed there.
That group turned out to be a bunch of frat boys -- an interesting challenge for four females who usually only played females -- and one of the things that the ST did to help us be a little braver in our portrayals was running that scene purely by candlelight. Not being able to see each other very well made a surprising amount of difference, even though we all knew exactly who was saying what.
Another thing that helped was focus. We were all pretty good at keeping the extra chat to a minimum (which isn't at all possible with some groups, I know), so we rarely broke character once we'd started. It made the atmosphere a little creepy, in this case, but it also made for a very effective scene.