My Friend is Sad is an Elephant & Piggie book by Mo Willems (of The Pigeon and Knuffle Bunny fame). It stars elephant Gerald and his best friend Piggie. Gerald looks sad, so Piggie decides to cheer him up. She disguises herself as a cowboy (Gerald loves cowboys), but he is still sad. She dresses up like a clown (a funny, funny clown), but that doesn’t work either! Piggie enters in full robot costume (a cool, cool robot mind you), but Gerald seems even more depressed than he was originally. Finally Piggie tries to reason with Gerald, but as soon as he catches sight of her he is instantly happy! He gives her a big hug and tells her all the amazing things he just saw. How could one be sad around a cowboy, clown, or robot, Piggie wonders, but Gerald lets her know all those great things mean nothing without a best friend to share them with!