The article aims at discussing the most characteristic linguistic devices thanks to which Marek Koterski performs stylization into the colloquial Polish language in Day of the Wacko (2002). This ﬁlm is very popular not only with the demanding elite audience but also a statistical Pole because apart from diﬃcult inter-textual references, the ﬁlm also plays with the language of everyday communication. The ﬁlm director tells about a subjective, colloquial experience of the world by the main character – Adaś Miauczyński, by means of diﬀerent experiments. They have been analyzed in this study with the use of methodology developed by both structural linguistics and cognitive linguistics. Thus, among the most essential endeavors used byMarek Koterski, we can list the following: colloquialization and vulgarization, breaking correct syntactic order, introducing word formative peculiarities and inﬂectional disorders. Exaggeration of mechanisms ruling the colloquial Polish language makes two main characters – Adaś and the Language, decide about Day of the Wacko popularity.