When starting a new game, press down repeatedly at the 1-player/2-player select screen.
More Challenge
Highlight Cheat Mode and press B, A, Right, Right, A, Left, A and X("BARRALAX"). All the DK barrals will be gone.
50 Lives
Highlight Cheat Mode. Press Y, A, Select, A Down, Left, A, and Down("YASADLAD")