Ubisoft recently announced that Scott Pilgrim vs. The World will receive the DLC treatment. The DLC will be released simultaneously with the film's DVD and BluRay release date.
The DLC will add Knives Chau to the playable characters roster, a free-for-all arena battle, (Joystiq uses the phrase Super Smash Bros Lite), and a dodgeball mode.
Ubisoft was also quick to add that with the DLC a title update will be released that will rebalance the "average joe" difficulty, fix several bugs, and introduce drop-in/drop-out co-op. The co-op additions is for offline play only. Ubisoft told Joystiq that there were no plans to incorporate online multiplayer into the game.
The price will be 160 Microsoft Points and no word on achievements.