This month marks 20 years since Mo Willems published his first picture book, "Don't Let The Pigeon Drive The Bus!" It has sold more than 6 million copies and received a Caldecott honor. But last weekend, readers got to see and hear a brand new side of the bossy bird. As NPR's Isabella Gomez Sarmiento reports, the Pigeon made his operatic debut at Washington, D.C.'s Kennedy Center.