Who is the antagonist in no more dead dogs?

In "No More Dead Dogs" by Gordon Korman, the antagonist is primarily the character of Mr. McNulty, the overzealous drama teacher. He is determined to produce a play based on a book that the protagonist, Wallace, criticizes for its treatment of dogs. Mr. McNulty's rigid adherence to his vision and his disdain for Wallace's opinions create conflict throughout the story, positioning him against Wallace's more honest and humorous perspective.