Select the 'Secret Code' option in 'Main' menu and enter this codes.
Unlock Art Gallery:
Dr. Wani, Dr. Wani, Dr. Wani, Dr. Wani
Unlock Bird's Nest Costume:
Lilly, Lilly, Lilly, Lilly
Unlock City:
Berry, Berry, Berry, Berry
Unlock Doom's Temple - Level 1:
Dr. Wani, Lily, Dr. Wani, Lily
Unlock Doom's Temple - Level 2:
Lily, Lily, Lily, Frogger
Unlock Doom's Temple - level 3:
Berry, Frogger, Frogger, Frogger
Unlock Dr. Wani's Letter:
Finnius, Lumpy, Berry, Lumpy
Unlock Dr. Wani's Mansion - Level 1:
Lily, Lumpy, Lily, Berry
Unlock Dr. Wani's Mansion - Level 2:
Dr. Wanni, Frogger, Frogger, Finnius
Unlock Elder Ruins - Level 1:
Dr. Wani, Dr. Wani, Lily, Lily
Unlock Elder Ruins - Level 2:
Frogger, Finnius, Berry, Frogger
Unlock Frogger on Moon:
Finnius, Finnius, Finnius, Finnius
Unlock John's Letter:
Dr. Wani, Berry, Lily, Finnius
Unlock Lobster Costume:
Finnius, Dr. Wani, Lumpy, Frogger
Unlock Masted Ship Costume:
Lumpy, Lumpy, Lumpy, Lumpy
Unlock Opart's Letter:
Lumpy, Frogger, Lumpy, Berry
Unlock Sealed Heart - Level 1:
Lumpy, Dr. Wani, Lily, Lily
Unlock Sealed Heart - Level 2:
Lumpy, Frogger, Frogger, Lily
Unlock Secret Admirer's Letter:
Frogger, Dr. Wani, Lily, Dr. Wani
Unlock Ship Costume:
Frogger, Frogger, Frogger, Frogger
Unlock Skull Costume:
Frogger, Lumpy, Lily, Frogger
Unlock WHCinc's Letter:
Berry, Frogger, Frogger, Lumpy