Challenges

Challenges is a new mode in Brawl. Each time you complete a certain task, a box breaks open revealing something to unlock (for example, a Stafy trophy appears, then how you unlocked it below), once a box breaks, bokes around that one turn red, and you'll be able to how to unlock that, but you can't see the unlockable.

There's also Golden Hammers that you can use to break boxes you're having trouble with. Once a Golden Hammer is used, it never returns. So use it wisely.