Picture Books for the Very Young
The Jolly Postman by Janet Ahlberg ISBN: 9780434925155
The Jolly Postman delivers cards and letters to various fairy-tale characters. He has a letter of apology for the three bears from Goldilocks, a postcard from Jack for the giant, a solicitor's letter on behalf of Little Red Riding-Hood for the wolf who ate grandma, and so on. There are six envelopes in the book, each containing letters, cards, etc.
The Very Hungry Caterpillar by Eric Carle