King Kong 2: Ikari no Megaton Punch/Secrets

Stage select code
At the title screen, enter the following sequence:

When you start the game, you can press on the second player controller to instantly advance to the next numerical world at any time, or you can press  on the second controller to pause the action of the game.

Continue code
At the game over screen, press in order , and you will be able to continue from the start of the world where you left off.

Secret ending message
During the ending, a baby Kong will appear on the screen and give you the peace sign. At this time, press and hold throughout the entire staff credits roll, and wait for the final screen to appear. If you held the buttons down, a secret message will appear, "KIMI WA TENSAIDA 573" which roughly translates to "You are a genius."