Shroob Castle

Shroob Castle is the corrupted version of Peach's Castle set in the past after it was taken over by the Shroobs. It is the setting of the final chapter in Mario & Luigi: Partners in Time. The Save Album refers to it as Peach's Castle (Past), despite the fact that Princess Shroob has complete control over it. However, name "Shroob Castle" does appear within the game, as it is used in the dialogue on the Koopa Cruiser, so the name is official. It houses some of the strongest enemies in the game.

Appearance
The castle towers are changed into tall purple mushrooms, along with all the pillars and bushes. The castle itself glows purple. Inside, a lot of the castle seems the same as the original, only darker, with the Shroob emblem and more violet in coloration. The map resembles the one of the present-day castle. Glowing purple mushrooms grow all over and a giant statue of the castle's ruler, Princess Shroob, can also be found here. Shroob saucers fly around the exterior of the castle. Beneath the castle is an underground cellar, and unlike the Shroob castle, it has the same music as the cellars in the present-day castle. It has a few enemies, most of them being Shroobsworth, Shroob Rex and Soul Bubbles. A regular Chain Chomp pesters Mario, Luigi, Baby Mario and Baby Luigi here as well.

Music
The music in Shroob Castle is a key-shifted arrangement of the Shroob theme, which plays in the opening scene as well as while the four Bros. are aboard the Shroob Mother Ship. No music plays in the room of the time hole; the music starts only after the player enters through the gate, which is blocked off until the player defeats the Elder Shrooboid at the Star Shrine.

Trivia

 * By using a series of glitches, it is possible to enter Shroob Castle after learning the Bros. Ball technique from Toadsworth and Toadsworth the Younger. This way, it is technically possible for the player to defeat the final boss while having only collected two Cobalt Star shards.