In April 1990, Sega commissioned its AM8 R&D department to create a character who would replace Alex Kidd as the company's mascot, as well as compete against Nintendo's flagship character, Mario. The idea of an egg-shaped character became the basis of the visual design for Dr. Robotnik/Eggman. In creating the "bad guy" for the Sonic series, the development team wanted a character who was "the opposite of Sonic;" a character who represented "machinery" and "development" to play on the then-growing debate between developers and environmentalists. The character was also designed to be easy for children to draw.
The English instruction manual for his debut game Sonic the Hedgehog described the character's full name as "Doctor Ivo Robotnik", while the original Japanese version's instruction manual for the same game called him "Doctor Eggman". It wasn't until 1999's Sonic Adventure that the character was called both "Doctor Robotnik" and "Eggman" in the English version, with all following English releases to date referring to him as "Doctor Eggman". Yuji Naka has explained that "Robotnik" is the character's true last name while "Eggman" is a nickname taken after his shape. Since then, Sega of America has listed his identity as Doctor Ivo "Eggman" Robotnik at least once, and has recognized the first name Ivo as recently as 2011. Despite that, Sega of Japan does not acknowledge an official complete name; the Japanese Sonic Channel lists his full name as unknown, and his in-game profile in Sonic the Hedgehog 4: Episode II lists his real name as a mystery.Eggman is described as being a certifiable genius with an IQ of 300. His fondness for machines has also made him a renowned authority on robotics. Ultimately, his goal is to conquer the world and create his ultimate "utopia", Eggmanland (alternatively known as the Eggman Empire or Robotnikland or Robotropolis). He selfishly never gives up on this matter, and does not care for others' opinions. He considers those who would interrupt his plans a prime threat. His abominable laughter and maniacal declarations contrast his self-professed softer side. Although Sonic has always ruined his evil plans, Eggman begrudgingly holds a secret respect for his determination.
In the majority of video games set in the Sonic the Hedgehog universe, Eggman has served as the main antagonist. Most of the Sonic video games that were released before 1998, the year in which Sonic Adventure was released in Japan, featured Eggman as the final boss that the player fights at the end of the game. Eggman also appears as a boss who the player must confront at the end of almost every level in most of the 2D Sonic games, and in Sonic 3D. In each game in which he makes multiple appearances as a boss, Eggman fights the player using a different machine each time he appears. In most of the 2D Sonic games, the player had to hit Eggman eight times in order to defeat him and move on to the next level or next boss. In most three-dimensional Sonic games since the release of Sonic Adventure in 1998, Eggman may serve as a boss at one or more points in the game, although he usually does not serve as the final boss. Many of the final bosses in these more recent Sonic games were former allies of Eggman who then betrayed him, while others were a third party that had no connection with Eggman whatsoever. Eggman has often formed temporary alliances with Sonic and others to help them defeat these foes.
Dr. Eggman debuted in the 1991 Mega Drive/Genesis platform game Sonic the Hedgehog under the name of Dr. Ivo Robotnik (Dr. Eggman in Japan) where he attempted to collect the six Chaos Emeralds and hoped to turn all of the helpless animals inhabiting South Island into robots under his control. Sonic manages to defeat Eggman and returns peace to South Island.
He returned in the immediate sequel, Sonic the Hedgehog 2, where he once again sought the Chaos Emeralds, of which there were now seven. He attempts to collect them in order to create the Death Egg, a huge, orbital space station that bares his appearance, in order to achieve world domination. He attacked West Side Island, turning its animals into robots. He was intercepted by Sonic and his friend Tails who saved the animals and retrieved the Chaos Emeralds before the evil scientist. Sonic raided the Death Egg, defeating Robotnik again and sending the Death Egg crashing back to Earth.
In 1993's Sonic the Hedgehog CD, Eggman, along with his latest creation, Metal Sonic, travels to Little Planet in search of magical gems called Time Stones that have the power to control the passage of time. In both endings, Eggman is seen flying away with a Time Stone, but is shot down by a rock thrown by Sonic in the bad ending.
In Sonic the Hedgehog 3 and Sonic & Knuckles (both released in 1994), following the events in Sonic the Hedgehog 2, Eggman's Death Egg crash-lands onto Angel Island, causing critical damage to the ship. While repairing the space station, Eggman meets Knuckles the Echidna, whom he tricks into thinking Sonic and Tails are villains after the powerful Master Emerald that Knuckles protects with his life. Knuckles steals the Chaos Emeralds from Sonic and constantly interferes with Sonic's fight. Eggman is able to launch the Death Egg, but it fails to get into orbit before Sonic sends it crashing back down. If the player is playing Sonic the Hedgehog 3, the Death Egg explodes completely while falling to the ground. In Sonic 3 and Knuckles, it crashes into the Lava Reef Zone. In Sonic & Knuckles, Eggman later reveals his true plan to Knuckles after stealing the Master Emerald during a fight between Sonic and Knuckles and gets the Death Egg into space once again. With help from now-ally Knuckles, Sonic is able to chase the madman into space and Sonic completely destroys the Death Egg. Robotnik makes one last chance to escape with the Master Emerald, but is defeated by Hyper Sonic.