在这部我又十八喜剧/奇幻片中,大卫的爷爷在过81岁生日时许下了一个心愿，愿自己能重返18岁。一次，爷孙俩在车上嬉戏出了车祸，结果爷孙俩的年龄互换了，老人成了大卫，并到大学里重新体验了年轻人的生活。
By means of an accident the soul of David and his swinging grandfather get swapped. While the grandfather's body is still in coma, he enjoys having a young body again and repairs some facts in David's life, who he finds not to be self-confident enough.
重返十八岁。
