Enter the code during the 'Capcom' logo at the beginning of the game.
Effect
Code
Allows you to listen to the 8-Bit soundtrack without beating the game first.
Enter Down, Right, Up, Left, Y, B. A chime will ring to let you know you're successful.
Bonus level
Have a seven in any digit of your money total, then enter any level.
Easy "Look Ma, No Spats!" achievement
Before starting, begin at the left and work your way to the right to clear the chests to get them out of the way. It is easiest to start on the right side and pogo to the left. Instead of pogo-ing on the spiders, wait for them to come down and then go back up. This will give you enough time to slip under them. Use short bounces by releasing the pogo button then immediately pressing it again. This will help you avoid the thorns on the ceiling and pass by the spiders easier. Once you are at the other end, pogo on the rope and climb up. You will "Look Ma, No Spats!" if your feet never touched the floor in the underground section.