The lucky cat is a decorative item found when fishing. The lucky cat is a reference the to Japanese neko cat which shop keepers place these cats out side there stores and it brings good luck the that shop.
The luck cat is yellow and has a red bow one hand is waving and has a smile and whiskers on its face.
The cat is very similar to the old boot, canned bottle, and scrap mechanic duck as they are all obtained while fishing. Only the old boot is used as it can hold crops. The lucky cat has no purpose other then decoration.