Enter "xyzzy" as a case-sensitive name. Then, hold A and press Select to increase the medal count to 400. Hold A and press Select again to reset the count to 0.
At the title screen, press Left(5), Up(5), Right(5), Down(5), Select(5) to unlock all levels and bonuses. To access the sound test, hold A and press Left or Right to make a selection, then press Select to hear it. Select the "Scrapbook" option to view background information about the game.
When the title screen comes up, press left 5, up 5, right 5, down 5, and select 5 times. Go to the test image. Whoever you have for a character, it will come up in a close-up version.
View ending sequence
Enter "staff" as a case-sensitive name. Enter the snack shop to view the ending sequence. Note: This also unlocks the hidden credits level. Quickly jump twice to get on top of the low building that appears immediately before the programmer's credit. Then, jump up and keep jumping to the right on the clouds until you find a hidden message.