Unlock First Person Mode
     Pause gameplay, hold Left Trigger and press Y, B, Y, B.

Unlock Mutant Mode
     Pause gameplay, hold Left Trigger and press Y, B, X, X.

Unlock Squeaky Voices
     Pause gameplay, hold Left Trigger and press Y, X, Y, Y.

Unlock Welsh Mode
     Pause gameplay, hold Left Trigger and press Y, Y, Y, Y.

Enable Real Controls
     Pause gameplay, hold Left Trigger and press Y, Y, Y, B.