Now, all you gotta do is come up with some terrible backstory that even a monkey on a typewriter could come up with. I usually just take Bruce Wayne's past and tweak a bit here and there. For example:

Vincent the Hedgehog was born to two loving parents, until one faithful day when Dr. Robotnik murdered them when he was only 9. He was then taken in by a clan of lethal assassins, who trained him to become a powerful warrior. After 10 years, the clan instructed him to murder an entire village, to which he refused, remembering the pain he felt when his own family was killed. Angered by his refusal, the assassins challenged Vincent to a fight, in which Vincent won. He now uses his assassin training to fight Robotnik's army of robots, and one day avenge his parents.