No what happened is that he was originaly called Eggman, the in America they got someone to make a comic as a backstory. He made a comic about a kind scientist called Dri Ovi Kintobor who got transformed into the evil Dr Ivo Robotnik. From then on the Western games used Robotnik and the Japanese games used Eggman. But later on they phased out Robotnik and reintroduced Eggman.