Dr. robotnik (aka dr. eggman)

, also known by his real name, Doctor Ivo Robotnik, is the main antagonist of the Sonic the Hedgehog series, a comically obese scientist with an IQ of 300, and the de facto archenemy of Sonic the Hedgehog. In childhood, the young Ivo Robotnik looked up to his grandfather, Professor Gerald Robotnik, and believed him to be a great man, who had done his best to help mankind and was unfairly executed. From this, the young Ivo likely viewed the government as corrupt, and in any case, decided to follow in his grandfather's footsteps to become a scientist. But somewhere along the line, he became obsessed with the idea of a world under his rule, and using his unmatched mechanical genius, began his plans. Long before the first Sonic game, Eggman met the hedgehog, and the two became instant rivals. Over the years he created several deadly creations, and, realizing the hedgehog's determination was as fierce as his own in overcoming them, gained a respect for his adversary. When he accidentally found his grandfather's diary, he was led on an adventure that would show him that his grandfather was perhaps not as innocent as he had thought. Recently, his plans have been increasingly hindered by outside forces, but this has given him chances to show his hatred of things that would threaten the entire human race, and consequently threaten his plans.

He is a short-tempered, loud and pompous evil genius who is constantly planning to take over the world. However, his plans have always failed thanks to Sonic and his allies. Despite his intelligence, Dr. Eggman is horribly immature, throwing temper tantrums when Sonic throws the proverbial wrench into his plans, and, at times, seems to overlook crucial details in his plans, such as in the opening sequence of Sonic's story in the 2006 video game when he orders his robots to fire on Sonic while he is escaping with Princess Elise, failing to realize that they could possibly injure or kill Elise if they land a direct hit on Sonic. An example of his immaturity is in the ending of Sonic Unleashed, when one of his robots 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

He has built immense warships, such as the Death Egg and the Egg Carrier, as well as escape units such as the Egg Mobile. In fact, his most famous machine is an Egg Mobile with a wrecking ball attached to the bottom, which appears in Green Hill Zone in the first boss level. His plans to create the ultimate utopia, the Eggman Empire, are always in full swing, and he doesn't care where to create it -- in the end, he plans for it to encompass all of Earth. His abominable laughter and maniacal declarations contrast his self-professed softer side as a romanticist, feminist, and gentleman. Despite his and Sonic's constant feud, he has secretly developed a begrudging respect for the hedgehog. Although Eggman is a villain, he helps Sonic and co. when the world is at stake, most likely because if the world is destroyed, there would be nothing left for him to conquer.

However, despite his desire for world domination, he does have a human side, and does not appreciate senseless destruction and killing. Although at times, he seems to have no problem doing so himself. As shown in Sonic CD's Bad Futures, the "Eggman Empire" is full of senseless destruction, tyranny and ruin. In Sonic Unleashed, there is a possibility that he murdered thousands when reawakening Dark Gaia by splitting Earth itself apart.

Eggman's most well known ability is his masterminded plots and schemes which only fail due to Sonic and his friends. He is a remarkable scientist and engineer, as evidenced by the armies of robots he's created. Eggman is an incredibly skilled pilot: able to swoop missiles and lasers in his Eggmobile with skill rivaling that of Tails. Eggman has also shown some considerable physical strength. Despite his physical structure, Eggman is also very athletic; this is seen in many of the 16-bit era games, where there is almost always a point where Sonic chases him; despite his weight and Sonic's speed, he always manages to outrun his nemesis (one time he outran a speeding truck) long enough to reach his next escape vehicle or weapon. This trait of agility is carried on in Mario and Sonic at the Olympic Games and Sega Superstars Tennis. He also has a special sensor in his glasses that allows him to locate Chaos Emeralds. Jokingly, as an in-gameplay mechanic, it is also said that he is faster in running speed than Sonic himself as he always escapes his grasp in the Game Gear games. Although it has been proven, it is unknown whether he is still faster than Sonic, since he is almost always in his Egg Mobile. In Sonic Chronicles: The Dark Brotherhood he is the most handicapped character in the game, as having no out of battle abilities and only one tag move with Tails despite being useful for defeating robots during the chapter. These are the two POW moves he has: Eggman might have superhuman strength. This is hinted in Sonic Riders, where Eggman could break stone pillars and even statues.
 * Bombardment (エッグボム Egg Bomb): Eggman does an odd dance to summon an artillery barrage that leaves the foe sluggish.
 * Sabotage (ぶんかい Disassembly): Tails joins Eggman to quickly and aggressively dismantle a robot target.