James and Lukas Rodriguez

The following characters had significant roles in the American television comedy series Malcolm in the Middle, which was originally televised from 2000 to 2006 on the Fox Network.

Originally there were four brothers (although Malcolm's oldest brother attended a military school away from home, so Malcolm was still the middle sibling left at home). A fifth son was introduced in the show's fourth season, a boy named Jamie. The boys are, from eldest to youngest: Francis, Reese, Malcolm, Dewey, and Jamie. In the final episode, Lois discovered she was pregnant with a sixth child. In the third season, Francis travels home (to celebrate his father's birthday) with an Alaskan girl named Piama, and reveals that they are married.

During the first season, the writers decided to keep the family's last name a mystery. In the fifth season episode "Reese Joins the Army (1)", Reese uses a fake ID by the name of "Jetson" to lie about his age. In the series finale, "Graduation", Francis' employee ID reads "Nolastname" (or "No Last Name", a joke referring to the fact that the family name was never spoken aloud). In the same episode when Malcolm was introduced to give the graduation speech, the speaker announces Malcolm's name, but microphone feedback makes his surname inaudible, even though he does appear to mouth the phrase "No last name".

In the pilot episode, the name Wilkerson can be seen on the name badge of the uniform Francis is wearing at Marlin Academy. In the sleeve notes for the season 5 DVD released in Europe, the family is referred to as the Wilkersons in the description for the episode "Block Party". British television advertisements and some Fox promotional material also occasionally referred to the family as the Wilkersons, although this name was never spoken aloud in the series. In an early version of the pilot, Malcolm had an exchange of dialogue with a classmate, who claims to have overheard his parents talking about Malcolm's family and asks him what his last name is. When Malcolm responds, "Wilkerson, why?" the friend replied with the punchline, "Oh...who are the 'Pariahs'?"

Out of the show's six leads, Cranston, Muniz, Berfield and Sullivan were the only ones to appear in all 151 episodes.

Hal, played by Bryan Cranston (all 151 episodes), is the father of the family. Though relaxed in his parenting when compared to Lois, Hal has shown that he can slide into a disciplinarian when confronted by the boys' bad behavior. He comes from a wealthy family who resent his choice to marry Lois over Susan (an action also shared by Victor and Ida). Hal has a hard time making good decisions, which he often deferred to Lois. Despite the fact many of the neighbors hate his family, Hal blends in well with them. He loves Lois more than she loves him, never even thinking about other women. He is also very scared of her, even more than the boys are, which is why he often bribes their sons to take the fall for his wrongdoings. He is very neurotic and has a slight obsessive-compulsive disorder, and also enjoys unusual hobbies. Hal is also a sex addict, this was revealed in the episode "Forbidden Girlfriend" when Lois is taking medication and is unable to have sex for an entire week, it is mentioned again in the episode "Poker 2" when Hal tells his friends he has sex 14 times per week. It was also revealed that Hal was a chain smoker before quitting the habit. Hal's best friend is Abe Kenarban.

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