Doctor "Eggman" Robotnik was looking through his computer to find more about his grandfather Gerald Robotnik. He recently found out Robotnik Enterprises had a partnership with Aperture Science. Cave Johnson helped Gerald Robotnik in creating the Space Colony ARK. Cave Johnson wanted to use it for testing, but Gerald said he had his own plans with the ARK. As a result, Cave and Gerald disbanded as Cave needed to continue his work on Aperture. While hacking through the files, Eggman found out that Cave Johnson kept his association with Robotnik Enterprises a secret and the only work he ever shared was with Aperture. While doing more research, Eggman discovered that Johnson died at sometime in the late 80s, there is no exact date. He also discovered the story of his assistant, Caroline, who ended up running Aperture after Cave's death. Eggman found out that her mind was put into the Genetic Life-form and Disk Operating System (G.L.a.D.O.S). But soon after, she devastated the entire facility by releasing a deadly neurotoxin. He couldn't find any further information. He envied Caroline. He wanted to build his own version of G.L.a.D.O.S so he can live forever, but he realized there was a huge risk in that. Also, he thought that the perfect way to kill Sonic and his friends was to put them into the Enrichment Center.
The next day, Eggman was in his eggpod searching around the world for Aperture Laboratories. He wanted to make a deal with GLaDOS that he can give her more test subjects (Sonic and friends) and after the testing is over, GLaDOS would in turn give him the blueprints for an A.I body. After searching constantly for hours, he finally found the facility. It seemed to be reconstructed after the incident that nearly tore it apart. It looked perfect for testing again. He crashed into the side and got into the enrichment center. It was huge, Eggman thought. It probably stretched on throughout the world. He finally got to GLaDOS' lair. She saw him and said, "Who are you?"
Eggman opened the shield of his pod and jumped out and walked toward her, "In 1951, Cave Johnson helped my grandfather in building the Space Colony ARK. A space station that would contain the information of life and culture, along with artefacts. So, if society on Earth has slowed down. Astronauts can go there and learn how to bring society back from the ground up. I want to return the favour to you by giving you four test subjects to continue testing."
"I thought you looked familiar. I remember your grandfather very well. He was a pompous billionaire. You look a lot like your grandfather. Therefore, I assume you are no different from him."
"Please," Eggman said, bowing, "I want to help. After you've killed them during testing or if they finished testing, I want you to give me the blue prints to build an A.I body like yours. Do you accept?"
GLaDOS paused for at least 20 seconds and then uttered, "I accept."