30 Foot Shaggy is the main antagonist of the What's New, Scooby-Doo? episode, Big Appetite in Little Tokyo. It is a green, scaly, enlarged version of Shaggy Rogers who looks like a cross between Shaggy and Godzilla, which is intentional as he is in a Godzilla parody.
What's New, Scooby-Doo?
Shaggy is supposedly cursed after eating a pizza with a transformation spell cast on it. Shaggy starts to grow into a Godzilla-esque creature every time he goes to sleep and he starts eating everything in sight. The gang had to run from the Tokyo police because of this, as they wanted to capture the 30 Foot Shaggy.
Even though this was a classic "guy in a mask" scenario, the curse looked real because the real villain had the aid of Dogbot (a robot dog of Velma Dinkley's creation). Dogbot would chew through Shaggy's chains while he was sleeping to make it seem as if he had turned into 30 Foot Shaggy. It is ultimately discovered that the giant Shaggy is in fact a robot by the gang,when they cause the robot to slip and fall, destroying it and revealing its mechanisms.