戴维·塞维尔（杰森·李 Jason Lee 饰）是洛杉矶一名郁郁不得志的词曲作者，他不分白天黑夜，努力创作，但作品总也得不到唱片公司老板的赏识。某天，满腔愤怒的戴维在家中大发雷霆，这时，三只来自大山的花栗鼠艾尔文（贾斯汀·朗 Justin Long 配音）、西蒙（马修·格雷·古柏勒 Matthew Gray Gubler 配音）、西尔多（杰西·麦卡尼 Jesse McCartney 配音）闯入戴维的生活。戴维惊讶地发现，这三个顽皮胡闹的小家伙不仅会说话，而且还能和声唱歌。于是他和小家伙们达成协议，它们可以在家中居住，但是必须演唱戴维创作的歌曲，妙趣横生的故事也由此展开……...
A mad scientist grandfather invents a genetic transformation machine and his 4 year old grandson accidentally turns his body into that of a 30 year old man. Baby Bobby escapes and runs around town as his siblings try to catch him before their parents get back from vacation AND before the bad guys get to him first. The machine is worth a lot of money and they only have a day before the machine loses its capabilities to change baby bobby back....
Three girlfriends, neglected and mistreated by their husbands, plan to take revenge on them with the help of an experienced man in this type of job....
