Music 3000
Hidden skin 1
At the main menu, press Select, Left, Right, Left, Right, Left, Right, Left, Right, Left, Right, Left, Right to unlock hidden skin 1.
Hidden skin 2
At the main menu, press Select, Left(2), Right(2), Left(2), Right(2), Left(2), Right(2) to unlock hidden skin 2.
Hidden skin 3
At the main menu, press Select, Left(3), Right(3), Left(3), Right(3) to unlock hidden skin 3.
Hidden skin 4
At the main menu, press Select, Left(4), Right(4), Left(4) to unlock hidden skin 4.
Hidden music track
At the main menu, press Select, Up, Down, Left, Right, Up, Down, Left, Right, Up, Down, Left, Right to unlock a hidden music track.