Hedgehogs may seem unlikely heroes, but teenage Sonic barreled full speed onto the video game scene in 1991 after his release by Sega. Sonic battled the evil Dr. Robotnik for Chaos Emeralds that would save the world from the doctor’s pollution. The Sonic the Hedgehog series was developed first for Sega Mega Drive/Genesis by the Sonic Team and the franchise has since sold many millions of copies.