Start a new game, and at the player-select screen, continually press Down on the control pad. If you did the trick correctly, a Music Test option appears that lets you listen to all the tunes in the game. Press Left or Right to cycle through the selections. Start a new game and at the gameplay-mode screen, keep pressing down until Music Test and Cheat Mode appear. Highlight Cheat Mode, then enter the following button presses.
50 Lives: Press Button Y, Button A, Select, Button A, Down,
Left, Button A, Down
No DK Barrels: Press Button B, Button A, Right, Right, Button A,
Left, Button A, Button X