This paper invites not to reflect on festivals as a celebration or a transgression but to observe them as «a play with» meaning and communication. The author considers the folklore as a genuine laboratory of observation of everyday life. He illustrates his analysis with the examples of the Binche Carnival (Belgium) and of Labour Day (1st of May) and gives an interpretation with G. Bateson’s concept of «play», as the English anthropologist had used to describe the play of animals at fighting. This leads the author to strongly insist on the small details of behaviours always imprinted with a “not” characteristic of ritual contexts.