These can be unlocked at the mainframe in the police station. Just go to "Codes".

Effect	Password
Caveman	ghhuj
Cheerleader	hhfgm
Circus Clown	yxjrtc
Deep Sea Diver	rmrqfn
Drakonas	vzhhdm
Forestman	kkrrwx
Mime	tfwfvs
Ninja Warrior	cxpnxx
Riot Vehicle	nqbsrp
Sentinel Disguise	mrphvq
Spartan Warrior	cqdhjs
Zombie	hvgtpg