Beat the game to unlock the "Extra Costume" option. Once you do that enter the following for the corresponding costume.

Effect	Password
Block Head	PutHere2FeelJoy
Don't Touch	TOUCH_MY_HEART
God of Thunder	GangsterGirl
Golden Rooster	cockadoodledoo
Heather Shirt	HappyBirthDay
Killer Rabbit	BlueRobbieWin
Onson	I_Love_You
Royal Flush	01_03_08_11_12
The Ligh	LightToFuture
Transcience	ShogyouMujou
Transform Costume	PrincessHeart
Zipper	shut_your_mouth