My friend Miriam Tell did a blog post about children's books with errors a while back, and this was my addition to her roster of mistakes: Leo Lionni's A Color of His Own contains the line "Goldfish are red." with a picture of an orange goldfish. And of course, the point that goldfish by definition, should probably be gold when making a book as simple as possible. Annoyed parent's design tip for children's book illustrations: You may invent your own world. However, your invented world should be consistent between words and illustrations.