@NinGabe: You can re-play levels that you have completed if you get a game over, but even if you get a game over you cannot re-play an already cleared castle, the only way to re-play a castle is in world 5, used a warp whistle in World 6, or in World 5 to return to world 5, so that way you can play all the clear level again including castle. or used the warp whistle in world 6 before going in the