John Bender
John Bender is the provocative bad boy of the group. He stands out as the protagonist among the ensemble cast. Stereotyped as a pot-smoking socially isolated "wastoid," the grungy-looking Bender taunts and torments the other students, particularly Claire, who he targets because of her privilege and popularity. Initially hostile, the other students develop sympathy for Bender when they learn that his aggression is a consequence of being raised by a verbally and physically abusive father. Bender also engenders sympathy for his mischievous behavior and rebellious confidence. He also protects the others from being caught out of the detention room by distracting Vernon away to the gym, not minding that he will get in even deeper trouble. Although Bender sexually harasses Claire throughout the day, Claire initiates a kiss with Bender, prompting him to suggest that a relationship with him would be an ideal way of getting back at her parents for mistreating her. As a token of their new bond, Claire puts one of her diamond earrings in Bender's hand before they say goodbye. He puts the earring in his pierced earlobe.
Claire Standish
Claire is a popular, beautiful, and wealthy girl who struggles with a troubled home life and social pressures. When the detention day begins, Claire's status at school means she only associates with people like Andrew, because he is a jock and therefore on the same elevated social tier. However, Claire's conceited nature comes into question over the course of the day as she relates to "weirdos" like Brian, Allison, and Bender. Claire resents both of her parents for using her as a weapon in their acrimonious post-divorce personal conflict. At the end of the film, Claire gives Allison a makeover, surprising Allison with her kindness. She also starts a relationship with Bender, who she finds appealing despite his harassment of her.
Andrew Clark
Andrew is a star wrestler at Shermer High School. He receives an all-day detention after spontaneously assaulting a weaker boy, explaining to the others that he did it because he thought it would make his father proud. When Allison says that Andrew's issue is that he can't think for himself, he agrees. Although Claire and Andrew are familiar with each other, Andrew is drawn to the far-more peculiar Allison, whose struggles with parental neglect engender empathy from him. At the end of the film, the two kiss in the parking lot before getting into their respective parents' cars.
Brian Johnson
Brian is a high-achieving, academically inclined and young-looking student. Stereotyped as a dork, Brian seems on the surface to be the most well-adjusted of the Breakfast Club. However, he reveals that the pressure to keep his grades high prompted him to consider suicide with a flare gun. When the flare gun went off in his locker, Brian was given detention. Brian reveals that his grades were impacted by his failure to make a functioning ceramic lamp in shop class, which he enrolled in because he thought it would be an easy A. At the end of the film, Brian writes an essay on behalf of the group. In his voiceover, Brian rejects the assignment, defying Vernon's authority.
Allison Reynolds
Allison is a social outcast who dresses in black and acts in a way that would suggest she has a social disorder. She spends most of the first half of the film not speaking, occasionally piping up with a spontaneous outburst. As the story progresses, Allison opens up to Andrew about her difficult home life. It turns out that her attention-seeking behavior results from parental neglect. She also identifies herself as a compulsive liar. After Claire gives Allison a makeover that reveals her beautiful face, she and Andrew are irresistibly drawn to each other. At the end of the film, she kisses Andrew before getting in her parents' car.
Richard Vernon
Vernon is the Shermer High School vice principal; he oversees the students' all-day Saturday detention. Vernon is strict toward the students, who immediately undermine his rules when he isn't watching. Vernon is the source of much of the movie's comic relief, repeatedly humiliating himself before the students. Vernon reveals a violent edge when he separates Bender from the group, threatening the teenager with physical harm. At the end of the movie, Vernon stands in the detention area and reads Brian's essay, which takes issue with Vernon's hostility toward the group.
Carl
Carl is the Shermer High School janitor. When he first appears in the film, he greets Brian by name. When Bender mocks Carl's job, Carl wins favor with Bender by saying that he overhears everything the students say and reads the notes he finds in the trash, referring to himself as the "eyes and ears" of the school. When Carl catches Vernon going through confidential student files, he asks him for fifty dollars to not tell on him for viewing the restricted material. In the next scene, Carl is drinking beers with Vernon. He encourages the principal to see the students as not being the enemies Vernon has built them up in his mind to be.
Andrew's Father
Andrew's father appears briefly in the film when drops off and picks up his son. Andrew hates his father for being an aggressive bully who puts immense pressure on Andrew to always win. At the end of the film, Andrew's father witnesses his son kissing Allison, glancing at the girl with a mix of amusement and surprise.
Claire's Father
Claire's father appears briefly in the opening scene of the film when he drops off his daughter for detention. Claire has a troubled relationship with her wealthy father, who uses her as a pawn in power struggles with his ex-wife.
Bender's Father
Although not shown in the film, John Bender imitates his father before the group. Bender portrays his father as obnoxious, low-class, and violent, suggesting that he hits both Bender and Bender's mother. Bender's father also burns his son's forearm with a cigar when he spills paint in the garage, and for Christmas gives his son a carton of cigarettes.
