An Exquisite Corpse is a surrealist writing game, where each person contributes a word to the sentence without being allowed to see any of the sentence before it. The outcomes tend to be weird, and sometimes serendipitously brilliant. "This Exquisite Forest," made by Chris Milk and Aaron Koblin (with a note off to the side saying "Made with some friends form Google + Modern TATE") is an animation game based on that original concept. Google posted a video on YouTube explaining the whole thing:
I haven't gotten a chance to play around with it yet (I don't have a computer that offers quite the right level of control at the moment) but the general idea is that people start off animation chains, and establish a theme. Other contributors then add animation to the end, branching off at whatever point they'd like. Each root animation branches into a tree of narrative, creating an exquisite forest.
I don't know if or how much of the previous animation is concealed or visible when you start. I imagine you'd get to watch all of it, then go on from wherever it ends, or maybe wherever you pause it. But maybe you get to pick a chunk in a timeline, and get a small clip leading up to your point.
I intend to explore it when I have a working computer, and will let you know how it goes.