Use the Enter Code Menu on the Computer in the Batcave

Password	Effect
ZAQ637	Unlock Alfred Pennyworth
JKR331	Unlock Batgirl
BDJ327	Unlock Bruce Wayne
M1AAWW	Unlock Classic Catwoman
HJK327	Unlock Clown Goon
DDP967	Unlock Commissioner Gordon
HGY748	Unlock Fishmonger
XVK541	Unlock Freeze Girl
NJL412	Unlock Freeze Henchman
UTF782	Unlock Joker Goon
YUN924	Unlock Joker Henchman
MVY759	Unlock Nightwing
CCB199	Unlock Tropical Joker