Infinite Continues Code
As posted by LiNkIn:
"When you lose all your lives and are at the continue screen, press up, down, right,
left and start and you will see that you didn't lose a single continue."
-Contributed by LiNkIn
Pause the game and press Left, Right, Down, Right, left, and R.
Have Every Power
Pause the game and press Down, Left, Right, Left, Up, L
Unlock All Levels
Pause the game and press Up, Left, Right, Down, Right, L. The levels will be invisible.
Pause the game and press L, down, left, up, down, R.
Soft Reset Code
Hold the A, B, Start, and Select Buttons to quickly restart your game.
-Contributed by Momorpher.