Godard wrote the script as he went along. He told Truffaut "Roughly speaking, the subject will be the story of a boy who thinks of death and of a girl who doesn't." As well as the real-life Michel Portail, Godard based the main character on screenwriter Paul Gégauff, who was known as a swaggering seducer of women. Godard also named several characters after people he had known earlier in his life when he lived in Geneva. The film includes a couple of in-jokes as well: the young woman selling "Cahiers du Cinéma" on the street (Godard had written for the magazine), and Michel's occasional alias of Laszlo Kovacs, the name of Belmondo's character in Chabrol's 1959 film "Web of Passion".