Play as the Bosses
At the main menu screen, hit L, R, Up, L, L, Down, R, R, and Start.
Extra Options
At the game-select screen, hit these buttons to gain advantages:
Extra two attribute points: L, L, L, R, L, R, L, and R.
Extra four attribute points: Up, Right, Down, Left, Down, Right, R, and R.
Extra six attribute points: Right, Down, Down, Left, Up, Right, L, R, L, and R.
Nine continues: Left, Right, Left, Right, L, L, R, R, and R.
Disable dizzies: Down, Down, Left, Up, Down, Down, Left, Up, R, R, and L.
Disable throws: R, Right, L, L, Left, Left, R, and R.