South Park

Master cheat:
Enter ZBOBBYBIRD to unlock all codes (invincibility, infinite ammo, all weapons,and stage select) and multi-player characters.

Chef in multiplayer mode:Enter YLOVEMACHINE as a code.
Wendy in multiplayer mode:Enter BCHECKATACO as a code.
Terrence in multiplayer mode:Enter SRAFT as a code.
Phillip in multiplayer mode:Enter PPHAERT as a code.
Ned in multiplayer mode: Enter JHAWKING as a code.
Mr. Macky in multiplayer mode: Enter ACHEATINGSBAD as a code.
Officer Barbrady in multiplayer mode: Enter DELVISLIVES as a code.
Big Gay Al in multiplayer mode: Enter GOUTRANGE as a code.
Starvin Marvin in multiplayer mode: Enter MSLAPUPMEAL as a code.
Mr. Garrison in multiplayer mode: Enter VDOROTHYSFRIEND as a code.
Pip in multiplayer mode: Enter EFISHNCHIPS as a code.
Jimbo in multiplayer mode: Enter QSTARINGFROG as a code.
Ike in multiplayer mode: Enter HKICKME as a code.
Ms. Cartman in multiplayer mode:Enter KALLWOMAN as a code.
Mephisto in multiplayer mode:Enter NGOODSCIENCE as a code.
Alien Visitor in multiplayer mode:Enter TMAJESTIC as a code.

To get this game:
http://www.gamecave.com/default.asp?source=uddm&sku=021PSXSOUTHPK
(Information from Cheat Machine)