A lot of this is tied to one of the game's mechanics called the Butterfly Effect. [...] During some of these choices, a small butterfly icon will appear in the upper right side of the screen. This indicates that the Butterfly Effect is underway. Pulled straight from chaos theory, the butterfly effect has it so that any one small change can bring about larger changes further down the road. For the purposes of Until Dawn, any one choice you make can have you going down any one path, eventually ending up at one of any of the hundreds of endings.

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So opening the wrong door, picking up the right clue, or saying something when you should have said something else will take you down your own path. There's a good chance that your path and ending will be nothing like your friend's path and ending. As the game progresses, there's a good chance that two people won't see the same scenes or hear the same dialogue.

Believe it or not, Supermassive shot and recorded every possible scene and outcome for these branches and endings. They believe that being able to experience your choices adds to the suspense and horror of Until Dawn so they went to the trouble of auditioning 200 actors before getting to their current cast, which includes TV star Hayden Panettiere. They wanted only top actors to fit with the high definition capture and high volume of voice work required. From what I saw, they've done a nice job with both the casting and capture.