Probably a Narwhal — Shelley Moore Thomas

Friendship is the winner in this hilarious contest between a girl who blames a narwhal for her mess and the narwhal who materializes to defend himself.

This girl's room is an amazing mess between the pies, the paints, and the giant rainbow splashed across the wall. She swears that she didn't make the mess--in fact, it was probably a narwhal. They make pies all the time, don't they? But when a real narwhal magically appears, the girl finds herself in a battle of wits with a creature who's every bit as feisty and funny as she is. Can she convince this creature that a narwhal made the mess? Can the narwhal convince her that she knows nothing about narwhals? In the hilarity that ensues, girl and narwhal discover they were destined to be best friends.