Guitar mini-game
Go to the screen where you choose your song. Press various controller buttons to display little icons on the screen that make the song do different things:

"Hide" icon
Press Red, Blue, Green, Blue, Red, Green for hidden mode. When the bars get to the middle/top area, they disappear making it very hard to hit them correctly.

"FF" icon
Press Red, Green, Blue, Pick(2) for fast forward mode. This makes the bars scroll faster.

"SFF" icon
Press Red, Green, Blue, Pick(2), Red, Green, Blue, Pick(2). The bars will scroll even faster.

"Random" icon
Press Blue, Green(2), Red, Green, Pick for random mode. Some notes will be randomized.

"SUD" icon
Press Green, Red, Blue, Green, Blue, Red, Pick at the mode selection screen. Notes will appear closer to the play line.

"Little" icon
Press Red(3), Green(2), Blue(3), Pick at the mode selection screen. This mode only allows two chords.

Skip intermission sequences
During an intermission sequence, hold Triangle