Head Canon
South Island is his world's version of Japan. My Sonic is from South Island and sometimes speaks Japanese.
The voice I have chosen for my Sonic is Jun'ichi Kanemaru.
He owns a Sonic Hero Chao named Maurice, that stays with, and is cared for by Sonic's parents.
He had a home made plush hedgehog that looked like his father named Geoffrey, Jay for short, from his childhood, to provide comfort while his father was away in The Great War. Sonic gifted this plush to Tails [@Goldkitsune], to help him over come his fear of thunderstorms.
Sonic is a excellent singer. He also plays the electric guitar.
He thinks he has great home repair skills. He doesn't.
He also thinks he can cook really well. He can't.
Sonic never says Good bye. He'll say later, so long, see you soon, ect. To him Good byes feel final. Forever.
Sonic keeps a journal where he writes about his travels and pastes post cards and photos from these places.
Sonic keeps small trinkets from places he has been. They are most often kept in his back pack.
Sonic has a dislike for the G.U.N Organization, ever since they hunted him as a fugitive, and then as they deemed Sonic a chaotic risk, since he often defies laws and goverment regulations.
Ladies make him shy and awkward, despite his 'always cool' demeanor.
Deep water terrifies him.
He once mentored a small snow leopard named Cloe, when she needed family.
His peach coloured parts are actually furry.
While growing up in the Acorn Kingdom, Sonic's hero other then his father was Johnny Lightfoot, for his ability to be so fast. Sonic vowed he would be that fast some day, and would practice running when he could. Others teased him saying that a hedgehog would never be able to run as fast as a rabbit.
Sonic has no place of his own. Living outdoors, or in over night shelters from the elements, he has no permanent location, since he's always on the move and would never be there anyway.
Sonic has a scar on his chest, just under his fur, from surgery preformed by a MV Dr.Faust, after Sonic met his demise in battle, at the hands of Mephiles.
Sonic's fear of water and lack of ability to swim, stems from him almost drowning in the Acorn Palace fountain, while playing as a child in the garden. It was not an accident as deemed, but a plotted out attempt on his life by Julian Kintobor who would later be known as Robotnik/Dr. Eggman. It was his father, Jules that saved him.Sonic acknowledges that SEGA is a corporation on Earth that he works with/represents. Other SEGA characters he interacts with are viewed as co-workers respectively.