Get the wing cap on top of the castle and rush to the cannon area. Run and dive into the base of the tree farthest from the castle. This should make you able to slide down underground. Swim quickly under the castle, and jump out on the small step near the waterfall, but make sure you’re still inside the castle. Facing away from the waterfall, triple jump and fly to a spot past the door, and ground pound on the slanted floor area. Again, you’ll need to be inside the castle. Now face away from the bridge, and triple jump as high as you can. Navigate to the area behind the entrance to the castle. This glitch is very difficult compared to some of the others in the game, so it takes a lot of practice. If you go through the door from this side, you’ll still end up in the castle like you would normally.