Fat Guys are enemies that appear Super Mario World 2: Yoshi's Island.

Super Mario World 2: Yoshi's Island

Fat Guys appear as rather enlarged versions of Shy Guys that appear across Yoshi's Island. They appear primarily in Super Mario World 2: Yoshi's Island. Fat Guys are invulnerable to jumping attacks by Yoshis, but they can be swallowed by them. When this happens, Fat Guys are turned into abnormally large eggs, that have the same effect as POW Blocks when thrown.

Paper Mario

Main article: Gourmet Guy

Gourmet Guy from Paper Mario

One very hungry fat guy is found in the Shy Guy Toy Box in Paper Mario, 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 in the game, this Fat Guy demands that Peach bake him a cake or he'll report her to Bowser's guards.

This Shy Guy is not named Fat Guy, but goes by the name of Gourmet Guy.