Get to Donut Plains 2. Go to the area with the pipes, jump up, and go though the last pipe in the line. Put the key in the hole and go and push the green button. Go back to Donut Plains 1 and get a feather. Keep going until reaching the green wall. Run up the wall with the feather and put the key in the hole. Go to the level that is now open. Get to the P button, pick it up, and carry it to blocks. Set it down and push it. Go through the coins and get the key. Put it in the hole and go to the Ghost House. G to the area where you get the P button. Go to the brown door, push the button, and get on boxes. Jump and climb the vine, then go though the silver door. Defeat the big Boo, go to the star, and get the key in Everyone Down. When you get to the bottom right level, go though the Star transporter and go to the Castle.

Jump down from the edge after you complete the Haunted House that you came to from the water. Go to the tube and enter it to get to a cliff by Bowser's Castle. Press A + B + X + Y + R + L to jump off to Bowser's Castle.