Please note VGF's cheat codes have relocated to the main page.
Classic Mode for Multiplayer
Press (Right C) twice at the Title screen.
(Thanks to kdnana@hotmail.com)
Bonus Multiplayer Map
Score a minimum of 50,000 points at the Pier Pressure bonus round. A message will now advise you that a new map has been unlocked. Save your game and quit. Restart, then choose the Multiplayer option at the main menu to locate the new bonus map.
(Thanks to kdnana@hotmail.com)