Xiaolin Showdown Cheats
If you want to unlock new costumes, level up the rank from Grass Hopper in Training to Wudai in Training. For certain ranks it will unlock new costumes: Monk costume Showdown costume Robot costume Street costume
After beating Mala Mala Jong in the last level of Adventure mode.
By getting at least halfway through the game to fight the Jack Spicer Robot. Defeat it to unlock Jack as a playable character.