the Knives Chau add-on pack for Scott Pilgrim vs The World, which adds the titular, ever-pining youngster to the game's cast of characters, along with a PvP arena, special dodgeball mode and drop-in, drop-out offline co-op, but it won't do you any good. At least right now it won't.
Those who've already downloaded the DLC are reporting that they can't access any of the new goods at all. At this point, accessing the DLC seems dependent on a title update. We've contacted both Microsoft and Ubisoft for clarification on the issue and will let you know what we find out.