These are all the possible skins you can get for Crash. Wearing a type of skin allows you to knock-out the creature your skin is from, then jack him immediately. Ex: If you wear the Spike Skin, you can knock him out in one hit, then jack him.

Effect	How to unlock
Battler Skin	Jack 35 Battlers
Bratgirl Skin	Defeat 130 Brat Girls
Doom Monkey Skin	Defeat 500 Doom Monkeys
EE-Lectric Skin	Jack 50 EE-Lectrics
Goar Skin	Jack 30 Goars
Halloween Skin	Complete 50% of the game
Koo-Ala Skin	Defeat 150 Koo-Alas
Magmadon Skin	Jack 50 Magmadons
Ratnician Skin	Defeat 200 Ratnicians
Rhinoroller Skin	Jack 30 Rhinorollers
Scorporilla Skin	Jack 15 Scorporillas
Shellephant Skin	Jack 15 Shellephants
Sludge Skin	Jack 50 Sludges
Snipe Skin	Jack 50 Snipes
Spike Skin	Jack 50 Spikes
Stench Skin	Jack 50 Stenches
Valentine Skin	Collect all Gold Idols
Voodoo Bunny Skin	Defeat 200 Voodoo Bunnies