Mr. Fitzgibbon
Mr. Fitzgibbon is Paul and Billy's father, and the husband of Mrs. Fitzgibbon. He is the farmer that owns the land where Mrs.Frisby's summer home is. In the book, he is the cause of the problem because he plows the land where In chapter 24, he tells his family (and in doing so Mrs. Frisby) about Henderson's hardware store and the exterminators from Nimh coming to kill or capture the rats.