9岁的乔治这天迎来了一个弟弟——小白鼠斯图亚特。这是他爸爸妈妈从孤儿院领回来的可爱精灵，会说话，有智慧，并且很希望有自己的家。然而，乔治却不喜欢斯图亚特，不愿意和他作伴。斯图亚特为此颇为犯愁。更令它处境不妙的是，它成为了肥猫眼中的佳肴，在虎视眈眈下过着冒险的生活。 　　乔治参加了一个航模赛，但是他却一路遭到挫折，先是父亲没能帮他做好模型，当模型好不容易做成了，遥控器却在比赛那天被别人踩坏。在乔治每一次陷入困难的时候，正是斯图亚特机敏勇敢的出手相助，让乔治顺利过关。斯图亚特努力的付出，终于被小乔治接纳，这只小白鼠在乔治家中得到了温暖的归属。In New York City, you would come across a small house, home to a family known as the Littles. You would happen to think of them as the nicest family you'd ever meet. One day, Fredrick and Eleanor, both parents and Littles, ho to and orphanage to find a brother for their son, George. While at it, they meet Stuart, a small, but charming mouse, who apparently, is human-civilized. They adopt him, and everyone, even George, loves him. But there is one problem with Stuart's life, Snowbell, the Little family cat, who wants him. But when trouble starts up almost immediately, Stuart must make it back to his home-before snowbell's friends find out about him