The series follows a dysfunctional working class family and stars Frankie Muniz in the lead role as Malcolm, an adolescent who tests at a genius level. While he enjoys his intelligence, he greatly resents having to take special classes for gifted children, which are mocked by the rest of the kids at school and called "Krelboynes", referring to the clumsy and nerdy lead character from "The Little Shop of Horrors". Jane Kaczmarek plays Malcolm's overbearing, hotheaded and stubborn mother, Lois, and Bryan Cranston plays his immature, manic, but loving father, Hal. Christopher Kennedy Masterson plays eldest brother, Francis, the trouble-making son who, in earlier episodes, was in military school, but eventually marries and settles into a steady job. Justin Berfield is Malcolm's dimwitted older brother, Reese, a cruel bully who tortures Malcolm at home, even while he defends him at school. Erik Per Sullivan plays younger brother, Dewey, who is people smart, musically talented, and concerned about his well-being. In earlier episodes, the show's focus was on Malcolm, but as the series progressed, it explored all six members of the family more. Another character, Jamie (James and Lukas Rodriguez), was introduced as the fifth son of Hal and Lois at the end of Season 4.