Get Multiplayer Extra Maps
Go to the first map and go to languages/voices. Pick the RAYMANIAN language and do not validate. Press and hold L1 + R1 then press L2, R2, L2, R2, L2, R2

Get Baby Soccer map
Before a game ends Press and hold L1 + R1 then press L2, R2, L2, R2, L2, R2

Extra Cheats
In any map go to the sound menu and highlight the Mute option but do not validate. Press and hold L1 + R1 then press L2, R2, L2, R2, L2, R2