Enter the following at the Cheat entry screen:
ZBOBBYBIRD Unlock all cheats! ACHEATINGISBADMr. Mackey in multiplayer BCHECKATACO Wendy in multiplayer DELVISLIVESOfficer Barbrady in multiplayer EFISHNCHIPSPip in multiplayer GOUTRANGE Big Gay Al in multiplayer HKICKME Ike in multiplayer JHAWKING Ned in multiplayer KALLWOMAN Ms. Cartman in multiplayer MSLAPUPMEAL Starvin Marvin in multiplayer NGOODSCIENCE Mephisto in multiplayer PPHAERT Philip in multiplayer QSTARINGFROG Jimbo in multiplayer SRAFT Terrence in multiplayer TMAJESTIC Alien in multiplayer VDOROTHYSFRIEND Mr. Garrison in multiplayer YLOVEMACHINE Chef in multiplayer
Thanks to Revolution readers SeAn SaMmOnS, Mike Spangler, Joe, and Corey Zick!