The following password combinations are entered at the 'Password' screen.

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 Stage 1:
Dr. Wani, Lily, Dr. Wani, Lily

Unlock Doom's Temple Stage 2:
Lily, Lily, Lily, Frogger

Unlock Doom's Temple Stage 3:
Berry, Frogger, Frogger, Frogger

Unlock Dr. Wani's Letter:
Finnius, Lumpy, Berry, Lumpy

Unlock Dr. Wani's Mansion Stage 1:
Lily, Lumpy, Lily, Berry

Unlock Dr. Wani's Mansion Stage 2:
Dr. Wani, Frogger, Frogger, Finnius

Unlock Elder Ruins Stage 1:
Dr. Wani, Dr. Wani, Lily, Lily

Unlock Elder Ruins Stage 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 Painting:
Lumpy, Lumpy, Lumpy, Lumpy

Unlock Sealed Heart Stage 1:
Lumpy, Dr. Wani, Lily, Lily

Unlock Sealed Heart Stage 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