Boo! Were you scared? The Scarecrow sure hopes so. Dr. Jonathan Crane was so interested in studying the effects of fears and phobias that he decided to put on a creepy scarecrow costume and be a super-villain. The fear gas that he uses makes people imagine that their greatest fears have come to life, leaving them helpless until it wears off. Bat-Fact: The Scarecrow’s biggest fear? Getting caught by Batman again.