Sonic 1 - Eggman makes his debut! This round-bodied genius villain has kidnapped and enslaved tons of little animals by making them into robots! Sonic steps him and chases him into his base at Scrap Brain Zone and finishes him off in a showdown against his piston machine. Eggman escapes.
Sonic 2 - Eggman repeats his last stunt, but there is more to it! He has enslaved animals working on his newest idea, the Death Egg. Sonic chases him all the way into space and battles his giant eggrobo. The Death Egg explodes and plummets down. Sonic escapes.
Sonic 3 - Eggman has landed on the floating island where he meets Knuckles, guardian of the Master Emerald. He tricks him into thinking Sonic is the bad guy and makes Knuckles work for him while he tries to get the Death Egg moving again. Poor dumb Knuckles.
Sonic & Knuckles - Sonic continues chasing Eggman with Knuckles getting in his way. Knuckles finally catches on to what Eggman is doing when Eggman steals his Master Emerald. Sonic goes Super and chases Eggman into space to retrieve it. Poor Eggy, he was so close.
Sonic Adventure - Eggman shatters the Master Emerald and releases the ancient liquid god Chaos. He plans to give Chaos the chaos emeralds to power him up and use him to take over Station Square and make it into Eggmanland. Unfortunately for him, Sonic and the whole gang plus a bunch of new characters are on the move to stop him, and on top of that, Chaos isn't a simple obedient creature. Far from it. Eggy takes a real lickin' this time around.
Sonic Adventure 2 - Eggman breaks into a military base and releases Shadow the Hedgehog, his grandfather Gerald Robotnik's creation. Along with him and Rouge the bat, he plans to collect the chaos emeralds and use them to power the Eclipse Cannon, a powerful cannon in space that he tests on the moon - and blows half of it away. Unfortunately he didn't know his grandfather went absolutely nuts after losing his sweet little Maria, and set a trap involving a giant Biolizard and a crashing space colony heading toward Earth. This time Eggman has to work with Sonic and his crew to stay alive and keep everything from being destroyed. Working with your rivals - harsh!
Sonic Heroes - Eggman's creation from Sonic CD comes back to bite him in the ass, hard. He is locked in a cell on his Egg Fleet and sends for help from the Chaotix detective agency to set him free. Meanwhile, Metal Sonic is out impersonating him and taking on Sonic and the crew. In the end, Metal becomes super powerful and Eggman doesn't think he can be stopped. Obviously he is still underestimating the power of Sonic and his team. The game ends with him running from the Chaotix to avoid paying them the rescue fees.