 Like Inkpen's Kipper the Dog for slightly older readers, Wibbly Pig has been published internationally and has sold millions of copies worldwide.The series are generally published as "board books", books with thick cardboard pages which are easier for very young children to turn and also more durable and easier to clean than normal books.Some of the Wibbly Pig books also have activity features such as flaps which can be lifted to reveal additional art.