Co-Writing for the Win

Ever played that game where one person starts a story before handing off the baton, then the next adds to it before shuttling it back or on to someone else? I used to play the story game with my family when I was a kid, and we always tried to throw huge obstacles in the path of the person who was next up (think a giant rock hurtling down at the character's head), mostly because it was funny but also because it was interesting. Co-writing's kind of like that, but instead of throwing each other ob...