一个男孩和他心爱的想象中的朋友能够在孤儿院里呆在一起，这些想象中的朋友的孩子已经长大了，不能被新来的孩子收养。

The gang must venture into a crazy imaginary world to rescue Frankie when she disappears inside a mysterious box.

Eight-year-old Mac and his imaginary friend Blooregard Q. Kazoo (or "Bloo" for short) often get into fights with his 13-year-old brother Terrence. When Mac's mother tires of this behavior, she tells him that he has outgrown his age to have an imaginary friend and must get rid of him. Crushed by overhearing their argument, except for Terrence, who is rather pleased, Bloo later comes across a TV commercial for "Foster's Home for Imaginary Friends"--"where good ideas are not forgotten," according to the motto.

范·维尔德即将度过他大学生涯的第7个年头，但毕业对他来说依然是那么地遥不可及。范非常满足于这种悠然自得的生活，他以及他那些英雄事迹——包括炮制并散播笑话、为慈善机构酬钱、以及激励那些受气包们等等等等——已经变成了校园里的一则传奇故事，在他周围聚集了一大帮崇拜者。范的父亲对这个不争气的儿子却是忍无可忍，他拒绝再为范支付学费。为了继续这种“永不毕业”的生活，无奈之下范只得转而充当派对策划人来自谋生路，学校里的女记者格文·皮尔森对范这号人物早就看不顺眼，这下她可逮住了机会，她处处留难范，于是两人开始了一场意志品质的较量。结果嘛，用脚指头也能猜得出来：这对不打不相识的冤家对头，在对方身上发掘出了许多自己所不具备的优秀品质，居然开始谈起恋爱来了！唯一的麻烦来自格文的男朋友、自我中心的男生会成员理查德，他决心不计任何代价阻止范继续成为校园里最受欢迎的风头人物。