Fred is a background fish best known for screaming "My leg!" in painful situations. He wears brown pants and is normally greenish-brown, but has also been colored blue, gray, and lavender. He first appears in the episode "Reef Blower," and his catchphrase is first used in "Boating School." He is featured prominently in the episode "My Leg!"
In most episodes, he appears as a greenish-brown-colored fish with light tan fins and black eyes. He wears brown pants and a black belt with a gold-colored belt buckle. He occasionally appears wearing a white collared shirt in episodes such as "Squilliam Returns" and "The Sponge Who Could Fly."
His character model appears lavender in "The Sponge Who Could Fly" and blue in numerous other episodes (e.g. "Something Smells"). Although the scleras of his eyes are usually white, they are yellow in "The Inmates of Summer."
His first appearance is the episode "Reef Blower." However, he is barely seen in the episode, as he is in a boat as SpongeBob zooms past him. He's most often seen dining at the Krusty Krab. He was one of the first two background characters seen in "Reef Blower," with Harry being the other.
He is the protagonist in the episode "My Leg!" where he tries not to hurt his leg in risk of getting it placed by a robotic leg. SpongeBob then tries to keep Fred's leg out of harm's way until he finnally reveals that he likes to be in the hospital so he can be with Nurse Bazooka (a nurse he is secretly in love with). So SpongeBob helps Fred by doing many dangerous attempts to purposely hurt his leg, but they just keep failing. When Fred finnally ended up in the hospital (after getting ran over by the ambulance twice), he sings the song "My Leg is in Love " to show Nurse Bazzoka how much he loves her. She enjoys the song and the two end up dating. This episode is Fred's biggest role yet.