Sonic became Sonic when (as a child, he was then brown) he burrowed in to a hill in his home zone. He discovered  an underground laboratory belonging to Dr. Ovi Kintobor. Dr Kintobor was working on a machine called the random omni chaos compressor (R.O.C.C), this machine was intended to absorb all the evil on planet mobius and compress it into the six chaos emeralds. Because sonic already had a lot of speed Kintobor used to time him and measure his speed on a treadmill until he eventually broke the sound barrier turning him blue. Later... Dr Kintobor was about to use the R.O.C.C machine, but before he felt hungry and went to the fridge, but all he found was a rotten egg, he picked it up and walked towards his machine. He tripped over some loose wires and accidentally activated the machine. The machine was unstable and exploded infusing Dr. Robotnik with the evil chaos energy and the rotten egg turning him into the evil Dr. Robotnik or Eggman. Robotnik vowed to take over the world and sonic vowed to stop him.