Princess Peach's Castle/Castle Dungeon

The castle dungeon is a cut area in the basement of Princess Peach's Castle, that was originally going to serve as a type of dungeon for the castle. Much like the Fourth Floor, the AI only makes it appear to experienced players. It appears behind a 20 star door and has 3 rooms.

Geography
The castle dungeon's layout is usually a main hallway leading to a painting that when entered goes to Fox Forest. To the right is what appears to be bars, which seems to be showing a small room with nothing in it. Taking the left path leads to the second room, which has a door and a painting of a Bully, which leads to Bully Beach. Entering the door takes you to the third room, with another wall that looks like bars, and some coins on the sides of the room.

Fox Forest
Fox Forest is a stage similar to Big Boo's Forest with seven stars, including the 100 coin star.. It's enemies include Goombas, Spindrifts, and a stage exclusive enemy called Yaps. They act similarly to Moneybags, by first disguising them-self as a bush, which are prominent throughout the level. Once Mario gets near them, they become fox-like enemies. How they attack is similar to Goombas by attacking when Mario is near. But they are much faster. There are trees throughout the level, and some of them have entrances. Most just lead to Coins but one leads to a star, and another leads to the whole interior of the tree. You have to climb up the tree in a Tick Tock Clock fashion. When you get to the top, there is a star. Five trees have secrets, and 8 trees have red coins. There is a Blue Coin switch in one of the trees. There is an NPC in the stage that looks similar to Mips that asks you to find their box. There are about 3 boxes in the stage but only one is theirs. After giving them their box they give you a star. The big tree in the middle's entrance opens up in the final star mission, and when you go inside it, you have to climb up a tree once again, but the interior is much bigger. Like last time, when you get to the top a star is there.

Bully Beach
Bully Beach is a level on the beach. As the name suggests, it's enemies are Bullies, Bubba, and Skeeters. You can defeat the Bullies with the multiple hot springs throughout the stage. The first star is underwater, blocked by a strong current that requires the Metal Cap to get past. The second one you get from defeating all of the Bullies in the stage, and the third one is from defeating the Big Bully. The fourth one is a Red Coin Star. The fifth one requires you to go down in the ocean again and find a treasure chest. Opening it gives you the star. The final star, not counting the 100 coin star, is gotten by swimming through an underwater maze.