Disney Universe has 45 different costumes available. You begin the game having access to nine of the costumes and unlock the 36 other costumes by rescuing guests to complete the locations in the various worlds. Be sure to get them all by unlocking them first, then purchasing them in the Costumes menu!
Tools
Each costume comes with its own unique tool which you can use to hit enemies and objects. As you are playing through the various levels, look for blue stars. They can be out in the open or locked up in chests. Find keys to unlock the chest and get the blue stars to upgrade your tool to the next level.
As your tool is upgraded by collecting blue stars, it gains extra powers which are released by ground slam attacks. At level 2, your tool releases an electrical charge that shocks nearby enemies. While they are stunned you can easily defeat them with another hit or two.
Upgrade to level 3 and your tool now has a fire attack, causing more damage to the area of the slam attack as well as firing off small fireballs that damage whatever they hit—including you. Be ready to jump up into the air to avoid those fireballs.
Finally, upgrade again to level 4 and your tool has a magical attack that damages enemies in a larger radius. Try to fully upgrade the tools for each of your costumes. All you have to do is collect three blue stars which can be accomplished while you play through the three levels in each location.