Mo Willems shares secrets to writing a children's hit book Mo Willems says his mantra is: "Always think of your audience, but never think for your audience." Mo Willems' new book, "That Is Not a Good Idea!" comes out April 23 Willems: "If you had an opportunity to drive a bus, would you do that?" The former "Sesame Street" writer and animator has written more than 40 books for kids Willems loves to see his fans draw his characters (CNN) -- Pigeons and mole rats are some of the stars of his stories. To a nation of toddlers, they are heroes. Children's author Mo Willems has written more than 40 books, and he's at it again. Willems, who started as a writer and animator on "Sesame Street," draws animals who aren't usually associated with starring roles. He depicts deep desires that he says all children -- and adults -- share. In "Don't Let the Pigeon Drive the Bus!" a bird pleads with readers to let him steer when a bus driver takes a break. His latest star is a fat goose in a story called "That is Not a Good Idea!" which also features a fox and a big bowl of soup. Willems is a novelty in his industry because he illustrates most of the stories he writes. Many of his books are fixtures on the shelves of children ages 5 and under. His name appears often on New York Times best-seller lists of children's picture books. Mo Willems says he tries to draw his characters so children can copy them. Young readers might also be familiar with the misadventures of Knuffle Bunny, a stuffed animal who is loved and lost in a series of books. Like all of Willems' protagonists, the bunny is easy for young fans to draw. Willems, who lives in Massachusetts, welcomes his fans' attempts to doodle their own versions of his characters. He told CNN how he creates classic children's tales from a garden of ideas, and encourages copyright infringement from his young fans. Below is an edited transcript. CNN: How did you come up with the notion that every 2-year-old wants to drive a bus? Willems: If you had an opportunity to drive a bus, would you do that? I mean, it's primal. It's absolutely primal. Have you ever walked by a bus and the bus driver isn't in it? I mean you really have to pull all of your power not to just jump in. We don't go, because we know we're going to get arrested, or we'll be late for work, and it'll be bad on our credit score. But if all that stuff disappeared, and you walked by a running bus without a driver in it, you would get in that bus. CNN: Have you seen some of your fans drawing the pigeon? Willems: Oh yes. Absolutely. I get a box every month filled with (letters from) kids infringing on my copyright. It is a legalistic nightmare, and a complete joy. And I post on my blog my favorites. But I just love it. I started out drawing Charlie Brown and Snoopy. And then I would have my own characters interacting with them. When I start seeing kids draw their characters interacting with the pigeon, you see that the creative crutch is going away, and that they're really becoming authors. For me, it's so important to doodle and draw. In my house, every night at dinner we have a big piece of paper that we put on our dining room table as our tablecloth and we doodle. I fear that grownups just don't doodle anymore. There is a day in everybody's life when they realize that they're not going to be a professional basketball player and they're not going to be a professional cartoonist. It's usually the same week. But people keep playing basketball. And they stop drawing. And I just think that that's such a waste. CNN: What inspires you? Willems: I'm very lucky to write for children, because I don't have to deal with popular culture. I can just deal with core fundamental issues: jealousy, love, hatred, sadness, joy, wanting to drive a bus. The fundamental core emotional things. And just asking questions like, 'How do you know when you're in control? What is a friend? What are relationships between people? These are all things that I haven't figured out yet. I'm very lucky in that I don't understand the world yet. If I understood the world, it would be harder for me to write these books. CNN: How do you create a timeless tale? Willems: That's a tough question. Besides dumb luck, I'm not sure. I do have a couple of rules that I place for myself in my books. The first is a mantra, which is: Always think of your audience, but never think for your audience. What that means is to leave it open to interpretation. I'm not telling things, I'm asking questions. And I'm asking questions that I don't necessarily have the answers to. The other formal thing that I do is that I make sure that the characters in my books -- in this ('That Is Not a Good Idea!') case, the chicks in particular -- are characters that a 4- or a 5-year-old can draw: infringe on my copyright with great ease. So a lot of my design work is reductive. I make drawings, then I try to take as many lines out, so that it's at its easiest to copy. CNN: Which comes first: the characters or the ideas? Willems: It all depends. A lot of people think of ideas as objects, or animals that you hunt. You go into the woods, you find an idea, you capture it and you bring it home. And ideas really are more like gardens. And every day, you're planting lots and lots of ideas. Some of them get eaten by birds, and never go anywhere. Some of them grow up to be really horrible things. Some wither and die. Every now and then, over time, some idea grows up to be big and beautiful and filled with fruit. You can cut that down and burn it for profit. So it's an evolution. CNN: What was the inspiration for your latest book? Willems: I think this one is about the question of: 'What is control?' And also about pacing, and suspense, and being helpless. In 'Don't Let the Pigeon Drive the Bus!' you yell 'No!' and you change the situation. The pigeon doesn't get to drive the bus because you yelled no. In this, you're yelling, 'That's not a good idea!' but it's still going to happen. You're seeing that truck wreck about to occur. It's about trying to change the world, and maybe not being able to. I don't know what it's about. And you know what? Frankly, it's not my job. My job is to make the book. You guys figure out the meaning. Come back to me, you tell me what it's about. CNN: What made you want to transition from television into writing children's books? Willems: Books have a lot more space for the individual. I'm very interested in things like failure, which most television executives don't think is a theme that they want to have. And just on a technical level, my books can be small. They can be long. They can be tall. A television is always the same size. I can be much more individual. "That is Not a Good Idea!" is released April 23.