By Mo Willems, Author & Illustrator. 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 There Is a Bird On My Head!, Gerald discovers that there is something worse than a bird on your head-two birds on your head! Can Piggie help her best friend? For ages 3 and up.