Watch Me Throw the Ball! (Elephant and Piggie Series) by Mo Willems

Gerald is careful. Piggie is not. Piggie cannot help smiling. Gerald can. Gerald worries so that Piggie does not have to. Gerald and Piggie are best friends. In Watch Me Throw the Ball!, Gerald is determined to teach Piggie that ball-throwing is serious business... but Piggie is just as determined to have serious fun.