He has authored the Pigeon series including the first book Don’t Let the Pigeon Drive the Bus! Which received the Caldecott Honor and The Duckling Gets a Cookie!? Which received an Irma Black Award Honor. He authored the Knuffle Bunny series which includes Caledcott Honors Knuffle Bunny: A Cautionary Tale and Knuffle Bunny Too: A Case of Mistaken Identity. He has authored the Elephant and Piggie series which has won several Geisel Medals and the Cat the Cat series as well as several standalone books.