
Secret Acts (First beat the game):
Get Secret Act 1 - Acquire an A or better on all 12 Acts.
Get Secret Act 2 - Complete Secret Act 1.
Different Costumes:
Push and hold R+L on the Character Select screen and choose a character.
Get Secret Characters:
Get Chi-Chi, Mai, Oozaru, Fu Lum, Piccolo - Complete Story Mode.
Get Neo Piccolo - Complete Secret Act 2.
Source:http://www.gamingcheats.com/psp/10657/dragonball-evolution-cheats.html