Willems, Mo Watch Me Throw the Ball! Disney/Hyperion, 2009. EARLY READER. Mo Willems adds a ninth book to the Elephant and Piggie series with an argument between the two friends about whether throwing a ball is hard work or if it can be a lot of fun. This odd couple is a very fun addition to any library collection! EL (K-3) – ESSENTIAL. Cindy, Library-Teacher.