The stage is pretty basic in design with two flat platforms separated by a tower in the center. The main stage element are the ! switches. There are 3 kinds that summon platforms in 3 different patterns. The red one makes a red ! block on each side. The blue makes a blue ! block on top. The green one makes two green ! blocks that extend from the left castle side. The ! blocks spawn a light item is attacked or jumped into from the bottom.
Banzai Bills will come occasionally and impact the stage. Fighters who touch it will get damaged. The Banzai Bill will explode after a little while. They have 3 ways of impacting the castle; from the left, from the right and from the top. All the ways still hit the tower.
In adventure mode, after completing Mushroom Kingdom, the player faces Mario and Peach on this stage. If the player completes Mushroom Kingdom with the timer with 2 seconds in last place, a cutscene will play and they will face Luigi. Beating him will also unlock him he hasn't been already.
Princess Peach's magnificent royal castle appears to be inhabited solely by the princess and a multitude of Toads. Bowser tried to steal the castle's Power Stars in Super Mario 64, and in Paper Mario, the surly archfiend actually lifted the castle into the stratosphere with his own filthy fortress.
- This stage's castle appears to be based off the one in Super Mario 64 and Super Mario 64 DS.