In the first map, in the Options Menu/Language/Voices, select the "RAYMANIAN" language (don't validate it), keep L1 + R1 pressed and do the following sequence: L2, R2, L2, R2, L2, R2. A new menu will appear with the three multiplayer bonus maps.
Baby Soccer bonus map
During a game (before it ends), keep L1 + R1 pressed and do the same sequence: L2, R2, L2, R2, L2, R2. The names of the players appear on the baby globox.
Game Shark Codes
Master Code (Must Be On) EC8398CC 1456E60A
Infinite Air 4CAFC2C6 14562433
Other cheats
In any other map, go to the Sound Menu, select the "MUTE" option (again don't validate it), keep L1 + R1 pressed and do the same sequence: L2, R2, L2, R2, L2, R2. A new cheat menu will appear.