King Bowser's Castle (Super Mario World 2: Yoshi's Island)

King Bowser's Castle is the final main level in Super Mario World 2: Yoshi's Island and Yoshi's Island: Super Mario Advance 3. Unlike in previous castles, the player controls the green Yoshi instead of the blue Yoshi.

Layout
When Yoshi starts the level, he is in an outdoor fortress area with a huge moon, hills and skinny trees in the background. He then needs to cross a long gap as Helicopter Yoshi. Along the way, Yoshi must avoid Skeleton Goonies; crashing into one will cause him to fall (usually leading to losing a life). Kamek also occasionally flies in during this time, trying to knock Yoshi out of the sky. If Yoshi makes it to the Yoshi Block, which is followed by a Middle Ring, Kamek will fly in for the last time in the area and look at Yoshi grimly. In the GBA version, he simply flies away.

The hallway inside the castle leads to a rapidly spinning roulette wheel with four doors numbered 1, 2, 3, and 4 to choose from. Yoshi must hit one with an egg, which will then drop to the floor and allow him to progress.

Door 1
Door 1 contains a single Shy-Guy, Mace Guys, Ball 'N' Chains, and lava pits.

Door 2
Door 2 includes nearly every Shy-Guy species, and at the end of that area is a door containing a Slime, who holds the key to another door that leads to the final room.

Door 3
Door 3 is notable for the appearance of Tap-Tap the Golden, where he chases Yoshi through a lava-filled cave path that autoscrolls. The "Castle Boss" music plays in this area, but in the GBA version, the "Room Before Boss" music plays instead. Yoshi can knock Tap-Tap the Golden back and into a pit with eggs, buying him some time. Tap-Tap the Golden will eventually reappear on screen, however. Eventually, Yoshi will reach a Warp Pipe to get away from him.

Door 4
Door 4 consists mostly of moving platforms that hold Coins (being a coin path where the player can get a lot of extra lives). All Red Coins and Special Flowers are in plain sight. The only possible threats are a few Gusties that fly through the stage and two Fly Guys at the end who carry 1-Ups.

Final room
All four areas lead to the final room before the boss battle, a dark autoscrolling playroom where the "Room Before Boss" music plays. Kamek appears here and attempts to attack Yoshi with his magic wand. If Kamek hits any of the blocks in the room with his magic, it will turn into a Fang, a Milde, a Shy-Guy, or a Star. If Yoshi makes it past Kamek's final shots, he will be awarded with a Middle Ring and a huge door that leads to Baby Bowser's room.

Kamek greets Yoshi, demanding he hand over Baby Mario. Soon, however, Baby Bowser awakens, aggravated at Kamek for being "too noisy". He then repeatedly Ground Pounds Kamek and kicks him aside, before noticing Yoshi and acknowledging him as a "gween donkey". He attacks Yoshi, trying to push Baby Mario off and ride Yoshi himself. If Baby Mario is saved afterward, Baby Bowser gets stunned. Yoshi must dodge Baby Bowser's Ground Pounds and Ground Pound the floor himself, creating a shockwave that can damage the young Koopa King.

Once Baby Bowser is defeated after three hits, Kamek returns, seemingly having recovered from his beating. He uses his magic on Baby Bowser, causing him to grow and fill the screen. Yoshi then finds himself outside in the now-destroyed room, and Big Baby Bowser appears in the distant background. For the final battle, Yoshi must nab red Giant Eggs from the Baron von Zeppelins that fly in, while avoiding falling rocks that destroy the ground and fireball blasts from Big Baby Bowser. During the fight, Big Baby Bowser will slowly advance from the background, and Yoshi must hit him with the Giant Eggs to knock him back. After a few hits, Big Baby Bowser will start charging at Yoshi head on. If he gets too close to the castle, the ground will be destroyed and Yoshi will lose a life. After seven hits, Baby Bowser is defeated, returning to his normal self. Kamek reappears and vows revenge before flying off with him. Yoshi then runs up to a small area where the stork and Baby Luigi are being kept. After that, a message says:

Thus, due to the marvelous team work of the Yoshi clan, the twins are reunited.

The captured stork is freed by Yoshi, and sets about his duty and finally makes the long awaited delivery!

'''Thank you, Yoshi! The twins will meet the parents soon!'''

The stork is shown flying above the clouds as the credits roll, finally able to make his delivery to Baby Mario and Luigi's mother and father. The game ends with an image of Baby Mario and Luigi being held by their parents, with text reading “The End” below. The screen freezes on the image once the music finishes and the system will need to be turned off or reset. The same thing applies with the GBA version unlike the other Super Mario Advance installments, although the game will still be saved after the ending in both versions.

Trivia

 * Baby Bowser is the only boss who must be defeated before Kamek casts a spell on him.
 * It's possible to land the last hit on Big Baby Bowser even if his charge destroys the ground Yoshi is standing on, which can result in a softlock or a glitched final cutscene.