Fiber
Fiber, or dietary fiber, is a material in foods which assists the digestive system in digesting food and other materials.
History
It was only seen in the episode "Mermaid Man vs. SpongeBob," when SpongeBob tried to end Plankton's mind control over Mermaid Man and Barnacle Boy. SpongeBob managed to get the controlled minions to consume the Krabby Patties, but the two weren't able to digest it until SpongeBob brought a concrete mixer filled with fiber and fed it to them, making them snap out of mind control.
In "Penny Foolish," Mr. Krabs was at the Discount Grocery Mart, and one of the items he bought was an industrial-sized pack of raw fiber.