Free Map Exploration:

After beating the game, do a soft reset at "The End" screen, then start a new game or continue using the password. Now you can walk through obstacles (mountains, rivers, sea). Your walking speed is increased, and you can walk even faster if you hold the B button. Also, there are no random encounters at all.

 

Picture And Sound Tests:

Enter these Japanese syllables at the password menu for the named effect.
 

Effect:                  Password:

Picture Test          Su Be Te No Te Ki Ga Mi Ta I Na

Sound Test           Su Be Te No Ki Yo Ku Ga Ki Ki Ta I Na