Play as one of the following characters on the indicated level to unlock their alternate costume:

Level: Legend Of Drunken Bastards
Play as Xiu Tan Sour and get 3 or more stars to unlock her alternate costume.

Level: Enter The Dino
Play as Monkey and get 3 or more stars to unlock his alternate costume.

Level: Revengeance Day
Play as Lucy Cannon and get 3 or more stars to unlock her alternate costume.

Level: Gigantic Crack
Play as Chop & Styx and get 3 or more stars to unlock his alternate costume.

Level: The Good, The Bad, And The Ugly Princess
Play as Ninja Fu Hiya and get 3 or more stars to unlock his alternate costume.

Level: Night Of The Living Fog
Play as Ninja Fu Hiya and get 3 or more stars to unlock his alternate costume.