"The 500 Hats of Bartholomew Cubbins" is a children's book written by Dr. Seuss. It tells the story of a young boy named Bartholomew Cubbins who lives in the kingdom of Didd. One day, he wears a hat that magically multiplies, leading to a series of humorous and chaotic events as he tries to remove them. As Bartholomew encounters various characters, including the king, he learns valuable lessons about identity and self-acceptance. The story is known for its whimsical illustrations and playful rhymes, making it a beloved classic in children's literature.