The objective of this study has been restricted to revealing the irony of Catholic dogma and its effect on the characters in Sister Mary Ignatius Explains It All for You. Christopher Durang assumes that the catechism, religious teachings of the church, can yield negative results on the individuals' psychology, they can get rather funny, even man, in this case, can lose his faith. The reasons are due to facts that religious teachers or catechists give their subjective explanations rather than base them on religious sources such as Bible; the realities of life are different from those which are taught at Catholic schools. This study involves Catholic religion, no other group is addressed. The study also aims, through the funny plays of the American playwright Christopher Durang, to reveal the negative effects of catechism on the individuals and thus answer the everlasting question: "How can religious dogma, which catechism can have, cause psychological problems rather than have relief on individuals". (C) 2012 Published by Elsevier Ltd.