You can enter any one of these while creating a license plate. 
Once finished inputting the code name make sure the okay button 
is highlighted first then press L1 + R1 + X.

HAWG Become a biker 
JASS Become a blind, mado-sachoism, donkey smoking a cigarette 
PHAM Become a butcher that is asian 
M1K3 Become a commando 
BRUZ Become a famous boxer 
B00B Become a female punk 
TFAN Become a gangster 
TATS Become a lady who has a tatoo everywhere 
MNKY Become a male punk 
J1MM Become a nasty corpse 
PIMP Become a pimp 
FATT Become a police officer in a higher position 
5WAT Become a S.W.A.T. team member 
B00Z Become a street bum 
HARA Become a working asian 
MRFU Become an asian that likes gambling 
FUZZ Become Johnson the police officer 
LOLA Become Lola 
B1G1 Become your female boss 
ROSA Become your partner 
HURT_M3 Become your partner but wearing lingerie instead