This paper is to examine Jeff Kinney's series Diary of a Wimpy Kid as a new literary genre, which has its own distinctive features. The popularity of the series underlies in its humorous feature which makes it very appealing especially to kids. The researcher has proven that the humorous amusement which Kinney's readers experience is to be attributed to one or another of the three traditional theories of humor: the Superiority Theory, the Relief Theory and the Incongruity Theory. In other words, an account of humor that cannot be attributed to a particular theory can be attributed to any of the other two. After defining each of these theories as well as throwing light on the challenges that faced each approach, the researcher has proven through some hilarious situations from the selected novel Hard Luck the validity and the equal efficiency of the three theories for the arousal of laughter without any discrepancy.