Sonic was checking out Zetti's hangout spot, and found a strange meat. He took a bite, thinking it was a hotdog, but eventually he realised that it was Mobian's meat, and his urge for cannibalism begun.
He still can eat normal food, and his personality is still the same Sonic. He's sane, cares about his friends, but his craving for meat of his own kind makes him act aggressive sometimes. He purrs when he eats, not even realising that. He would be very uncomfortable if he met another cannibal.