From LEGO Batman Wiki
Professor Jonathan Crane was a scientist who excelled in phobias. He would later become the vicious phobia criminal, Scarecrow.
Life before crime
Jonathan Crane's life was hard, he was a lanky boy who loved books. He was constantly taunted and bullied by his glasses, lanky frame, and lust for books.
As a young man, he got a job at Gotham University. The headmaster fired Crane for illegal experiments, and firing a gun in one of the classrooms.
Jonathan, in a rage, then walked over to the nearby costume shop and got ragged clothes and a wide-brimmed hat, like a scarecrow's. He then stitched his mouth up for extra fright. he then got a mask and doused it with phosphorus, a substance that glows in the dark. The scarecrow was complete.
Jonathan Crane as the Scarecrow was portrayed by Dave Wittenberg.