Secret Password
Once an Unlock Code has been entered in the secret room in the tutorial level, you may enter one or more Effect Codes of equal or lower level. These codes may be entered freely and without any specific method - there is no need to reset the combination lock at any time unless you need to enter another Unlock Code.
Entering in a correct Effect Code will cause a chest to appear from the purple brick pipe in the room. Simply walk into the chest to claim the prize. Certain chests (the wallpapers, for example) may be collected multiple times to alter the current effect. In particular and as an example, the Default Wallpaper chest will not appear until you have changed the current message border to something else.
Note that these codes will not work until the correct Unlock Code has been entered since entering the secret room.