Fat Guys are an overweight variant of Shy Guy featured mainly in the Yoshi's Island series. They first appear in Super Mario World 2: Yoshi's Island.
Super Mario World 2: Yoshi's Island[]
Fat Guys are invulnerable to jump attacks, although they can be swallowed by a Yoshi. In doing so, the Yoshi converts the Fat Guy into a Giant Egg. Fat Guys are featured in two colors, red and light green, neither of which have any difference in behavior from one another.
In Paper Mario[]
A very hungry Fat Guy named Gourmet Guy is found in the Shy Guy's Toy Box, where he asks Mario to bring him something to eat. After Mario gives him the Cake, Gourmet Guy runs around the room happy and leaves a path open, also dropping his Cookbook in the process. Later on, Fat Guy demands Princess Peach to bake him a cake and threatens to report her to Bowser's guards if she does not.