2011 is the year of season passes, a term that started with sports titles offering a years worth of content for a premium price. This has since migrated into just about every game genre as a way to get some savings on future, planned DLC releases. It seems that THQ is trying to help out their more loyal customers by giving away this content for free just for buying the game early.
If you pre-purchase the game on their site, for any platform, you will get the season pass which includes three downloadable missions for free. In addition to that pre-orderees will also recieve Professor Genki’s Hyper Ordinary Pre-Order Pack. Though I’m not certain what that pack entails, it is free, so why not take advantage of it.
The free season pass is a limited time offer however ending on the release date(November 15), so it’s best to get on that sooner rather than later to secure yourself some free DLC.