From the Super Mario Wiki
Gargantua Blarggs are massive Blarggs which resemble Nep-Enuts that reside in lava in Super Mario World 2: Yoshi's Island, Yoshi's Island: Super Mario Advance 3, Yoshi's Island DS, Yoshi's New Island, Yoshi's Woolly World, Poochy & Yoshi's Woolly World and Yoshi's Crafted World. These huge creatures attempt to block Yoshi's path by rising from the lava as the dinosaur approaches. To pass by a Gargantua Blargg, Yoshi must throw an egg at the monster's mouth. The fire creature will then sink into the lava, allowing Yoshi to continue his journey. However, they reappear after a few seconds. Unlike the smaller Red Blargg, Gargantua Blarggs can not be defeated with POW Blocks.
In the game Tetris Attack, a Gargantua Blargg appears as a ruler of the "Lava World", being allied with Flamer Guy. In here, as many other old enemies of Yoshi, was shown as a friend of Yoshi, being enchanted by Bowser to work for him. He replaces the fire fairy, Flare, from the original Japanese version of the game.
Another sub-species of these Blarggs also called Gargantua Blarggs appear as well. These Blarggs are much taller and can destroy dense rocks.
In Yoshi's Woolly World and Poochy & Yoshi's Woolly World, Gargantua Blarggs merely appear as an outline composed of an orange scarf. It takes three yarn balls to make the Gargantua Blargg hide back down into the lava. They mainly appear in the level Lava Scarves and Red-Hot Blarggs.
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