Hookbill The Koopa's Castle

Hookbill The Koopa's Castle is the final level in World 4 of Super Mario World 2: Yoshi's Island and Yoshi's Island: Super Mario Advance 3. As the name states, Hookbill the Koopa is fought here. This level's playable Yoshi is the blue Yoshi.

Overview
Blue Yoshi starts in a long corridor with Boo Guys, and a bucket hanging. After this corridor, the Yoshi has to use a bridge to across a lava pool, with a Hot Lips trying to harm Yoshi by spitting lava at him. The Yoshi also finds Koopa Troopas here, and it can use their shells to reach a Special Flower right above the lava. After the second Hot Lips, the Yoshi can use another shell to collect a Special Flower above the lava. The Yoshi also finds another bucket and a pipe spawning Boo Guys here. After the lava pool, the Yoshi needs to cross a long corridor, with Boo Guys trying to crush it with Tekkyū Dosun. Yoshi must destroy large blocks with eggs here, allowing him to reach a Door.

This door leads to a room, with Winged Clouds that form stairs when hit, and there are several Boo Guys operating Tekkyū Dosun. The Yoshi can also collect Red Coins here, as well as a Special Flower by passing through the flippers. Upon entering the door, the Yoshi finds a spinning wheel, which it must use to across a large area with thorns and reach a locked door. It can also use this spinning wheel to reach a bonus area in the ceiling, where it must defeat two Puchipuchi L to earn a single Red Coin.

To unlock the door, the Yoshi must hit a Winged Cloud in a narrow corridor using a shell, thus making a stair appear. The Yoshi must then use this stair to reach another door. Here, the Yoshi must ground pound a crate containing the key. Then, it must simply pass through the flippers to make its way back to the area with the locked door. After entering this door, the Yoshi needs to climb a tower while avoiding the Fishing Lakitu that tries to steal Baby Mario with its hook. Once the Yoshi reaches the top, it must enter a Warp Pipe, leading to an area with several rectangular blocks, which can be destroyed by throwing eggs at them. There are two Special Flowers along these blocks. By destroying one of them, the Yoshi is able to use a Spring Ball to reach the red door leading to the boss.