Elephant & Piggie: I'm A Frog! 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 I’m a Frog! Piggie has some ribbiting news! Can Gerald make the leap required to accept Piggie’s new identity?