Skins are different versions of the character Catbird there are three skins counting the default with two too unlock the second skin Black bird, you need to unlock fifteen crowns, to unlock a secret level at the end there will be a box with a question mark, touch it and you've unlocked the skin, the same thing goes for the third skin, Gold bird except you need twenty five crowns to unlock the secret level. Skins don't do anything except change your appearance.
NORMALThe appearance of the first skin is very simple it's just a cute little white catbird.
The second skin is virtually the same as the first but black the thing that sets it apart from the first skin, even more, is the fact the pixel lineart and the eyes of catbird turn a white to make the black stand out much more.
The third skin is like its name says gold but with white markings, another special thing about it is that when playing levels you can see little shimmering sparkles.