The fire that engulfs the bodies of these bat-like Keese makes them more dangerous than the standard type. They're capable of setting fire to anything they touch.
—Compendium entry on Fire Keese, The Legend of Zelda: Breath of the Wild
"Bodily excretions of a highly flammable waxy substance interact with the cell structure of this grub-dog's skin, causing a chemical reaction that produces extremely high temperatures. The skin benefits from a spongy cell structure that diffuses the surface heat, protecting the creature's inner organs. Due to the astonishing amount of heat produced by this beast, it should be observed with great caution."
—Olimar's Notes on the Fiery Bulblax, Pikmin 2
"A species of terrestrial snail coated in flammable mucus instead of the traditional shell. The creature stays lubricated through constant secretion of mucus so that the fires never reach its skin. The most fascinating aspect of these creatures is their instinctive ability to avoid causing widespread fires by carelessly brushing plants."
—Olimar's Notes on the Pyroclasmic Slooch, Pikmin 3 Deluxe
