Show and Tell -- Robert Munsch, Paperback

Ben wants to take something really neat to school for show and tell. What could be neater than his new baby sister? But his sister doesn't want to co-operate.

She cries in his backpack. She cries at the teacher. She cries at the principal, who decides she must be sick.

When they call in a doctor, she cries harder. Ben knows just the right person to call to help--his mom!