Sonic was obviously a hedgehog, taken into Green hills after a tragic accident from losing Long claw, an owl who took care of Sonic as a child. In Green hills, He eventually met two very nice people. Tom and Maddie Wazowski who took care of him. Late on, Sonic found two new friends, Knuckles the Echidna and Tails the fox. They were all under Tom and Maddie's care.

Sonic soon found a partner, another hedgehog named Shadow. Unlike the blue hedgehog, Shadow had black and red quills, red eyes, white chest fur, gloves like Sonic, inhibitor rings on his wrists and ankles with red and white shoes like Sonic's but bigger and help him run way faster as Shadow was stronger as well.

When Sonic introduced Shadow to Tom and Maddie, they knew it would be a lot of work to deal with another life form in the house as they already have to take care of Sonic, Tails and Knuckles which were a lot to handle.

Luckily, Tom and Maddie didn't have to worry much about taking care of Shadow since he could take care of himself except when in high places as they all learned Shadow's fear of heights. Sonic loved being around Shadow although he was usually having a serious or expressionless face, rarely smiling. "..."