Cheat codes:

Bird's Nest costume:
Enter "Lilly, Lilly, Lilly, Lilly as a password to unlock the Bird's Nest costume.

Painting:
Enter Lumpy, Lumpy, Lumpy, Lumpy as a password to unlock the Painting.

Ship costume:
Enter Frogger, Frogger, Frogger, Frogger as a password to unlock the Ship costume