Dr. Eggman, born under the legal name Ivo Robotnik, is the morbidly obese grandson of Professor Gerald Robotnik and cousin of Maria Robotnik. He is the main antagonist of every Sonic the Hedgehog franchise and the arch-nemesis of Sonic the Hedgehog. He is also the boss of Eggman Enterprises and ruler of the struggling Eggman Empire.
Much of Dr. Eggman's past is unclear. However, we know he is the grandson of Gerald Robotnik and cousin of Maria Robotnik. He has an IQ of 300 and dreams of running a robot-controlled society named Eggmanland.
Before the events of Sonic, Dr. Eggman captured Miles Prower in hopes of having a minion as smart as he is for his goal to take over the world. Sonic the Hedgehog rescued Tails and the two of them put a stop to Eggman's first evil scheme.
Eggman's second evil plan was to use a self-built Chaos Emerald-powered Ion Cannon to destroy Central City and cause the Guardian Unit of Nations and the government to fall, allowing him to take over the world. However, he was stopped by Sonic the Hedgehog.
Eggman wanted to obtain the 9 Keys of Shadows to summon the Dark Force to wipe the planet clean and give him a clean slate from which to build Eggmanland on, but Red stopped his nefarious plan.
Dr. Eggman wanted to use the Master Emerald to power his superweapon: the Death Egg. He sent Buzzsaw to steal it and Knuckles the Echidna went in pursuit before being captured by Eggman and imprisoned on the Death Egg. After being freed by Sonic, they took on Eggman and returned the Emerald to it's alter.
Eggman is short-tempered and cruel, but not afraid to crack a joke at the right time. He will do anything to take over the world, including taking lives.