Mr. Happy 是全世界最快乐的人，他住在快乐岛屿上，岛上住着快乐的小鸟，湖里鱼儿也快乐地优游着。但是，某天Mr.Happy却听见在快乐岛上听到不属于快乐岛上的声音，那就是抱怨声！怎么会有人在美好的快乐岛上抱怨、发牢骚呢？ Mr. Happy一看，原来是正在湖边钓鱼的Mr. Grumble在碎碎念！ Mr. Grumble想要找一件自己喜欢做的​​事情，于是Mr. Quiet建议他可以去钓鱼，但是爱发牢骚的Mr. Grumble这么爱碎碎念，湖里的鱼怎么可能会上钩呢！ Mr. Happy也希望Mr. Grumble跟他一样快乐，于是就帮助Mr. Grumble一同寻找会令他快乐的事情。他们拜访了好多人，Mr. Impossible、Little Miss Splendid、Mr. Nosey、Mr.Rush、Mr. Bounce、Little Miss Giggle...等等，但是一整天劳碌下来Mr.Grumble就是不停的发牢骚，没有一件事情是他感兴趣的，对于忙了整天的Mr. Happy来说，这一天还真是漫长！隔天一早，Mr. Happy的早茶都还没喝完，就火速的跑去找Mr. Grumble，告诉他一件他做了一定会开心的事情。 Mr. Happy到底是发现什么事情能够让爱发牢骚的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