Nintendo's line of Super Mario games include dozens and dozens of levels for us to explore, but in the end we're always left wanting more. Fortunately for us, this is where the lost levels enter the picture. For whatever reason, there are sometimes a few levels locked away in a game that are unaccessible through conventional means. Now an attempt to hack together a level editor for New Super Mario Bros. has led to the (re)discovery of a few demo stages that have not been seen since E3 2005. GameSetWatch has the details in an interview with teenage ROM hacker Treeki. As for the lost levels themselves, check these out:
I never get tired of reading about lost levels. Ask a developer about material cut from a game and you'll most likely get an answer back that involves a hazy half-memory of why that particular stage was cut from the final product, but the Internet will not settle for less than a complete documentation of excised material. We love our games, but sometimes we love to dissect them even more.