Sonic the hedgehog's arc nemesis. Eggman is just a nickname, his true name is Robotnik.
Dr. Eggman is a brilliant scientist, bent on world domination.
Throughout the Sonic Franchise, Eggman has played the main antagonist (with occasional acts of heroism), capturing wild-life and transforming them into his personal army. His reasoning for this came somewhat to light during the events in Sonic Adventure 2, where it was explained how his grandfather; Pr. Gerald Robotnik, was killed by G.U.N. for his experiments.