Hookbill the Koopa

"How c-c-can this b-b-b-be? How is everyone f-free? Well too b-bad, I'm j-just g-gonna have to stomp you."

- Hookbill the Koopa

Hookbill the Koopa is an enlarged Koopa Troopa in the game Super Mario World 2: Yoshi's Island and its remake. He is the boss of World 4 and resides atop the castle of that world.

A similar boss called Knot-Wing the Koopa appears in Yoshi's Wooly World and Poochy and Yoshi's Woolly World, as a recurring middle boss in even-numbered worlds. Knot-Wing is essentially a Koopa Paratroopa enlarged in the same fashion as Hookbill.

Super Mario World 2: Yoshi's Island
When Blue Yoshi and Baby Mario reach the bridge on which Hookbill is fought, a fog envelops the area, dissipating on the other side. Blue Yoshi and Baby Mario then encounter a normal Koopa Troopa and Kamek, who casts his magic on the Koopa. The Koopa Troopa retreats into his shell, which grows.

After the transformation is complete, Hookbill re-emerges from his shell. Walking on all fours, he creeps towards Blue Yoshi to attack him and Baby Mario. After walking on all fours for some time, he stands up and runs in Blue Yoshi's direction and lunges at the dinosaur. Blue Yoshi then must dodge the attack in order to avoid getting hurt. To defeat Hookbill, Blue Yoshi must first throw eggs at his head or arms. Jumping on Hookbill's shell or head will cause Hookbill to cough up eggs for Blue Yoshi to use in case his supply gets depleted. After four hits while on all fours or after three hits while on two legs, Hookbill will fall backwards and will be briefly vulnerable to attack. Blue Yoshi must jump on and then ground pound Hookbill's exposed stomach, delivering damage to Hookbill. After this (or after a certain amount of time passes), Hookbill will recover, retreat into his shell, and begin pounding the ground. He will then re-emerge, and the process will have to be repeated. Once his stomach has been pounded three times, Hookbill is defeated. His shell explodes and disappears, and Hookbill (with no shell and reverted to normal size) falls from the top of the castle.

Yoshi's Island DS
During the introduction to Yoshi's Island DS, Hookbill the Koopa makes an appearance alongside the other castle bosses in the game as the events of Super Mario World 2: Yoshi's Island are recapped.

Tetris Attack
Hookbill The Koopa reappears in Tetris Attack as one of Bowser's allies in the game and speaks with a stutter. Here, he takes Phoenix's place of the original Panel de Pon at Stage 9, and unlike other characters, Hookbill does not have a personal ally of his own.

Super Mario World 2: Yoshi's Island

 * Official Nintendo Player's Guide: Mists swirl around the castle high up in the mountains at the end of World 4. Yoshi finally makes it to the parapet, the mists clear, and Eeek! It's a giant Koopa Troopa! Fortunately, Yoshi keeps his wits about him and remembers that Koopa Troopas are most vulnerable when on their backs. Watch out, though. Hookbill has the unique ability to pull in his head and shell the opposition.
 * Super Power Club Cards bio:
 * Description: High in the clouds above his castle, this turtle seeks a dinner of Yoshi on the half-shell.
 * Favorite Fashion Tip: "Tortoise-shell frames are you, baby!"
 * How to Beat Him: Jump on Hooktail's head to make him cough up his eggs. When he stands on his hind legs, shoot him in the head, then power-dive on him when he falls on his back.

Trivia

 * The design of the turtle boss had several revisions during the development of Super Mario World 2: Yoshi's Island, earlier depicted as a shelled creature somewhat resembling Birdo.