Super Peach's Castle of Fury

Super Peach Castle is a Fawfulized version of Peach's Castle in the game Mario & Luigi: Bowser's Inside Story. Bowser must become giant to fight it. This boss is the last Giant Boss in the game. When Bowser follows the incomplete Dark Bowser out into the castle grounds, Dark Fawful arrives in front of Bowser, who gets annoyed. Dark Fawful then mentions how he needs more power. He also replies that Bowser's meddling has given him fury as large as the world, then taunts Bowser while saying "SUPER PEACH'S CASTLE OF FURY!". This commands the castle to transform into a giant Mecha, crushing Bowser. Afterwards, Mario, Luigi and Starlow go to the Rump Command and make Bowser giant again. He then fights the castle.

Super Peach Castle starts off the battle by creating a black hole that forms behind Bowser, making it so that Bowser must beat the vacuuming force of the black hole every turn until phase two of the battle starts. Shortly into the fight, the boss deploys a horde of Mechawfuls, which requires fireballs to defeat them. The Castle reacts to the flames by "ejecting all heated cargo," giving Bowser a Mushroom. After Bowser deals enough damage to the castle, phase two begins.

The castle fires an unavoidable laser beam, which instantly sucks Bowser into a black hole. The player must stroke right to make Bowser escape from the black hole. When Bowser successfully escapes, he launches towards Super Peach's castle, dealing damage. Super Peach's Castle tries to make a second black hole, but Bowser shoots a fireball at it, making the black hole go behind the castle instead. It then puts up a force field, preventing damage from Bowser's attacks. Bowser must try to launch Super Peach's Castle towards its black hole, then it launches itself towards Bowser. He must punch to deal more damage to the Castle in this phase. After a while, the Castle makes the black holes come closer to the adversaries, making harder for Bowser to attack. If the Castle is sucked into the black hole in this phase, it activates the Boo System, making it invisible as it launches itself toward Bowser, and he must time his punch to avoid damage. Alternatively, the player can time how long the castle takes to ram Bowser ahead of time in order to time the punch correctly.

Near the end of the fight, both Bowser and Super Peach's Castle are sucked into the Black Holes and Bowser must keep launching himself towards the Castle. The Castle releases spikes from its hands, damaging Bowser if he launches himself, but it retracts a little after. After the battle, Bowser successfully demolishes the castle, and moves on to defeat Dark Fawful and Dark Bowser. If the player fails escaping the black holes, and or Bowser's health falls to zero, both Bowser and the black hole will shrink, get smaller and smaller, and then disappear, leaving the player alone with a Game Over.