Dr. Jonathan Crane was a professor of Psychology at Gotham University, specializing in the psychology of fear. As he grew up he was bullied due to his bookishness and his gangly figure. He became Scarecrow to get even with the bullies at school. After his dismissal from Gotham University, for firing a bullet at a flowerpot to get his point across, he killed those people responsible for his dismissal.
Now, using odd gasses and his freakish costumes, The Scarecrow instills fear in all who see him.