| If there's an author and illustrator of children's books working today who is worthy of Dr. Seuss' mantle, he is Mo Willems. His best-selling adventures for young readers include "Don't Let the Pigeon Drive the Bus!" and the "Elephant and Piggie" series. Now, the New York Historical Society has brought together original art, sketches and drawings from his most popular books. Vinita Nair reports.