Martha doesn't share!
(Book)

Martha, the stubborn little otter, returns to master a new lesson. She overuses the word "mine, " until she is left performing magic tricks without an audience, putting on puppet shows with only one puppet, and playing Ping-Pong without a partner. Through the gentle encouragement of her parents, Martha realizes that she can have more fun if she shares. The watercolor and colored-pencil drawings focus on each character's body language and facial expressions. Through her scowl, up-turned snout, and raised eyebrows, Martha's feelings should be readily evident to youngsters and demonstrates that sharing isn't all that bad when you take it one (small) toy at a time.

Martha learns there are unpleasant consequences for refusing to share with her baby brother.