Berenstain Bears and the Spooky Old Tree, The (GBA)

Unlock level 2
Enter the following password at the password screen, its located in the second option at the main menu: Bug Squirrel Knight Knight

Unlock level 3
Enter the following password at the password screen, its located in the second option at the main menu: Squirrel Bug Knight Drawers

Unlock level 4
Enter the following password at the password screen, its located in the second option at the main menu: Drawers Drawers Knight Drawers

Unlock level 5
Enter the following password at the password screen, its located in the second option at the main menu: Knight Squirrel Squirrel Knight

Unlock level 6
Enter the following password at the password screen, its located in the second option at the main menu: Bug Squirrel Bug Bug

Unlock level 7
Enter the following password at the password screen, its located in the second option at the main menu: Squirrel Bug Knight Bug