While the Gamecube logo appears, hold Z to hear new sounds. Hold Z then about one second later hold A to hear another sound.
While the cube bounces down, hold A to form the "G" logo to spin it.
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.
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.