Mr. Happy 是全世界最快樂的人，他住在快樂島嶼上，島上住著快樂的小鳥，湖里魚兒也快樂地優游著。但是，某天Mr.Happy卻聽見在快樂島上聽到不屬于快樂島上的聲音，那就是抱怨聲！怎么會有人在美好的快樂島上抱怨、發牢騷呢？ Mr. Happy一看，原來是正在湖邊釣魚的Mr. Grumble在碎碎念！ Mr. Grumble想要找一件自己喜歡做的​​事情，于是Mr. Quiet建議他可以去釣魚，但是愛發牢騷的Mr. Grumble這么愛碎碎念，湖里的魚怎么可能會上鉤呢！ Mr. Happy也希望Mr. Grumble跟他一樣快樂，于是就幫助Mr. Grumble一同尋找會令他快樂的事情。他們拜訪了好多人，Mr. Impossible、Little Miss Splendid、Mr. Nosey、Mr.Rush、Mr. Bounce、Little Miss Giggle...等等，但是一整天勞碌下來Mr.Grumble就是不停的發牢騷，沒有一件事情是他感興趣的，對于忙了整天的Mr. Happy來說，這一天還真是漫長！隔天一早，Mr. Happy的早茶都還沒喝完，就火速的跑去找Mr. Grumble，告訴他一件他做了一定會開心的事情。 Mr. Happy到底是發現什么事情能夠讓愛發牢騷的Mr. Grumble露出微笑呢？

They're back Rediscover the zaniest characters you've ever met in this bestselling series which has sold millions worldwide. Just in time for Fall 1997's hot new animated TV show, Mr. Men and Little Miss "TM" are being relaunched in the U.S. Bright and charming, with easily recognizable characters and a small take-along format, Mr. Men and Little Miss "TM" books are easy enough for young readers, witty enough for humor-prone adults, and highly collectible for one and all. Great crosssover potential -- again Mr. Happy meets someone who looks just like him -- and his name is Mr. Miserable