I'M A FROG by Mo Willems (2013)
When Piggie pretends to be a frog, she has to explain to her friend, Gerald the elephant, what pretending is and why its fun to act like you're someone else.  Herald is very literal and takes some convincing, but finally decides he can also pretend.  He lets out a "Mooooooo" that takes over the whole page.  Young readers love Elephant & Piggie books because the vocabulary, along with the conversation, is basic and repetitive and always clever.  Willems also authored A BIG GUY TOOK MY BALL! (another Elephant & Piggie book) in 2013.
Lynette Suckow, Peter White Public Library