The Frogfish is a gigantic, red anglerfish that appeared in The SpongeBob SquarePants Movie and The SpongeBob SquarePants Movie (Video Game). It also appeared in the video game SpongeBob's Truth Or Square. In the SpongeBob SquarePants Movie was luring SpongeBob, and Patrick, in with an ice cream stand, much like how real frogfish uses lures on their tongue (or illicium) to lure in unsuspecting prey. SpongeBob was ordering the ice cream and he discovered it stuck to him, in fright he bit the substance attached to his arm, and ran from it, the frogfish then revealed itself and chased the Patty Wagon, almost to Combustion, but when it did get the wagon, it was eaten by a Giant Eel from the below trench, and was never seen again.
The Frogfish's tongue is purple and had a brown feline-like creature called Mister Whiskers, both of these masses could speak.
Stephen Hillenburg was fascinated by the habits of Frogfish, so he decided to add this one to the film.
If you look closely in SpongeBob's Atlantis SquarePantis, in the Snap Happy level, you can see a frog fish hanging to the ceiling, and SpongeBob states, "There's big and then there's REALLY BIG."
The bonus material on The SpongeBob SquarePants Movie reveals that the frogfish's tongue is an old lady selling free ice cream due to the fact by that being what would lure in SpongeBob and Patrick, as compared to the real frogfish having a tongue with the scent of fish food on it.