Level Skip
Press during gameplay Up, Sqaure, Triangle, Square, Triangle, Circle, Up.
Hidden Autumn Level
Go to the Autumn hallway. Then, look for the black wall and double jump through the wall. Then follow the hallway to the hidden level.
Play As Sam
Go to the sheep pen in the Starting Studio. Hold down R2 and L2, and press Down, Circle, Left, Square, Up, Square and Left.