The film is based on a series of immensely popular Swedish children's books, about the boy Bert, who is just hitting puberty and having the usual problems with it. But that's where the usual ends abruptly.

The first appearance on screen for Bert Ljung, a normal teenager who's diary Swedes have been able to follow in well over ten books now. As in the books, he fights spots, looks for girls, runs his moped, plays with his weird friends Ake and Erik, and a lot of other stuff teenagers are supposed to do.