Mr. Happy knows how to fix a bad day. But will he be able to help the other Little Men keep their smiles and optimism when the weather in the Land of Joy turns strange and gloomy?

The book teaches children positive thinking and various ways to deal with the challenges and disappointments of everyday life. The story presents simple steps for managing negative emotions, such as adapting, asking for help when needed, or simply thinking of reasons to feel grateful. There is also a basic vocabulary related to weather conditions.