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, though 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, cuffless 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.

Eggman is a short-tempered, raucous, pompous, and cruel evil genius who is constantly trying to take over the world. His primary motivation throughout most games is his psychotic belief of self-entitlement. Arrogant and narcissistic, he constructs his countless technological wonders in his own image to fuel his massive ego, usually reinforced by his goal of building the Eggman Empire, and doesn't care where he starts it. His narcissism is such that when he first discovered the Phantom Ruby, what it showed as his deepest desire was Eggmanland complete with various labels of his names and statues to himself, and was saddened when the illusion ended.

Although Eggman is a villain, he helps Sonic when the world is at stake; though the reason is always because he knows if the planet was destroyed, there would be nothing left to rule over. In some of his incarnations, he actually displays a begrudging respect of his arch-enemy, Sonic.

Despite his intelligence, Eggman can be very immature, throwing temper tantrums when Sonic manages to wreck into his plans. An example of his immaturity is in the ending of Sonic Unleashed, when his robot begins to insult him over his constant failures and calls him a loser; Eggman screams "Oh, shut up!!", attempts to kick him only to comically fail, and then chases him through the desert while making agitated noises and violently flailing his arms in an attempt to grab him.

(Vocal Direction: Deem Bristow/Mike Pallock)