In general, Eggman is depicted as being rotund in appearance. He possesses a dome-shaped head and no visible neck, a bald head, a bright red nose, and a very bushy mahogany moustache. During his early years, Eggman had a completely round torso with normal-looking arms and legs. Back then, he also wore a red shirt/jacket with yellow triangles (which can be described as either a collar or part of a cape, which can be seen on his back), with black pants with connected boots and silver-colored round buckles, white gloves, and mirrored pince-nez glasses.

In the present day, Eggman remains obese, but has become somewhat burlier, taller and less flabby with long, almost disproportionately thin arms and legs. He now wears both his tinted glasses and green-lensed goggles as headwear, through his mustache retains its length, density and mass. Gone are the cape and his suit-like clothes, in their place an elegant, red coat sporting two square metal buttons on both sides of the chest in gold. These buttons have white straps that run across the coat's sides to identical buttons on the back. The coat also has silver, zipper-like linings down the back, arms and front, yellow cuffs, and two extensions on the front that have large silver buttons. In addition, Eggman also wears white, cuff-less gloves on his hands and a pair of black pants with matching boots seemingly attached to them bearing circular plates on the both sides of the ankles and three square ones riding up the shin.

In Sonic the Hedgehog (2006), he was given a radically different appearance owing to the more realistic designs of the game. In particular, he has yellow bolt-like buttons on his red coat where the buckles were originally, as well as a slightly raised collar obscuring his chin. The moustache, while still bushy, also looks more groomed, and he also, while still overweight, looks very lean by comparison to his usual designs. His nose is also colored the same as the rest of his skin.