Instead of using both audio cords (red & white ones), use one of the DVD's Audio cords and one of the GameCube's Audio cords. This way, you can hear the game's music & the DVD's music. But remember, turn the game's music off in the options (if you can), and make sure you have the GameCube's Video Cord in and not the DVD's.
Alternate start-up sound
Power on the GameCube, then hold Z while the GameCube logo is forming to hear a different start-up sound.
Change Screen Refresh Rate
While powering on the system, hold B until the message "Would you like to switch to 50hz mode?" appears. This allows you to switch the screen refresh to match that of PAL games. If playing on a PAL system, the message will be "Would you like to switch to 60hz mode?", allowing the screen refresh to match that of NTSC games.
Control starting logo
While the cube bounces down, hold A to form the "G" logo to spin it.
DVD Music
You know how XBox can put music from your CD's onto the game, well I found out how you can do it with a GameCube.
First, you need all of these.
-1 Nintendo GameCube
-1 DVD Player
-1 TV w/AV slots (not a TV/DVD combo)
-Your favorite music CD
This is what you do:
Hook up the DVD Player (Audio only) to the AV Slots. Then, Put in your CD into the DVD. Set your track you want to listen to. Put in ONLY the Video AV jak from the gamecube to the TV. Then play your Game. Although you don't here the game sounds, you can listen to your songs while you play. Try playing music based on the game your playing. Example: "Ghost Busters Theme" while playing "Luigi's Mansion".
Game Boy Advance to Gamecube link option
This trick requires two Gamecubes, two televisions, and at least one Game Boy Player. The purpose of this trick is to eliminate the need for a Game Boy Advance and also use the special function it provides on a television screen. Attach the Game Boy Advance to Gamecube cable into the link cable slot in the Game Boy Player (without a game in it) that is attached to the other Gamecube (on which the game with the special options is played, such as the Tingle Tuner on Legend Of Zelda: The Wind Waker) or put in the required game that may be required for other options (such as the Metroid Prime and Metroid Fusion hookup).
Set system time and options
While powering on the system, hold A or hold A while the cube rolls around the screen. Alternately, turn on the Gamecube without a disc. Wait until the opening sequence is over and you will be able to set the time and date on the system, delete memory files (if there is a memory card inserted), and set the sound and screen position.
Spinning Cube
Turn the machine on and you will see a square bouncing down to form the G. If you hold A during this sequence as the square is bouncing down it will spin which looks very cool.