Doctor Robotnik, also known as Dr. Eggman because of his body shaped like an egg, is an evil scientist and a genius who aims to take over the worls using his robots and build the Robotnikland, where he would have his own empire. And he knows the only way do do it is having all of the powerful Chaos Emeralds. Despite of his I.Q. of 300, Eggman act as a child at the most of the time, and views Sonic as his archenemy
because he always seens to spoil his evil plans.
Eggman loves to build machines. Among his greatest inventions
there are the Metal Sonic, robot created after Sonic resemblance who also is able to copy his data, the Eggmobile, the little egg shaped ship he uses to help him move from place to place, and the Death Egg, a giant and powerful moon shaped space station. It also have his creator's face resemblance.