This article discusses the relationship between conventionality in language and humor. It puts forward a categorization of ready-made combinations, from collocations to discourse formulas, highlighting the mechanisms in which they are used to create humor. As ready-made combinations, they are fixed or semi-fixed expressions decoded as a linguistic whole. Humor is achieved by manipulating these combinations so as to cause a breach in the listener's/reader's expectations. Because mastery of linguistic conventionality is closely associated with fluency, and humor relies highly on a breach of conventionality, it is claimed that lack of fluency prevents full comprehension of humor.