From the Main Menu, choose Password and enter one of the following. The numbers correspond with how many times you press the Up button on each image.

Effect	Password
Go Out On A Limb Stage	06, 06, 02, 00.
I'm No Second Banana Stage	00, 00, 04, 05.
Jungle Legend Stage	01, 02, 06, 03.
Ship Escape Stage	05, 04, 03, 06.
The Jungle Is My Play Ground Stage	03, 01, 02, 03.