Fry Boy, Defender of the Krabby Patty is an alter-ego of SpongeBob SquarePants. He wears a superhero suit with two spatulas put in his belt. He has hair (which is weird, because SpongeBob doesn't usually have hair) and is able to throw Krabby Patties into someone's mouth. He was able to reverse the hypnosis of Mermaid Man and Barnacle Boy with Krabby Patties (and a hint of fiber). Fry Boy only appears in "Mermaid Man vs. SpongeBob."
He basically proves that Krabby Patties can save one's life, as it saved Mermaid Man and Barnacle Boy's (with some help from fiber).