Before certain missions (1, 6, 8, 9, 14), press L, L, R, R, then click the Left Analog stick, then the Right Analog stick before launch. You'll hear some funny business as a result.

Go to the mission select screen. Once there, click down the Left analog, then press BLACK, R, click the Right analog, then press WHITE, then L. This will unlock everything in the game.

To win the mission you're currently playing, click the Left analog, then press WHITE, WHITE, BACK, click the Right analog, WHITE.

To change the music, do this at the title screen: click the Left analog twice, then click the Right analog twice, then press L, R.