Protagonist
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Character Role Analysis
John Bender, Andrew Clark, Claire Standish, Brian Johnson, Allison Reynolds
All five of the main characters can be seen as one united protagonist. As individuals, many of them probably can't be seen as the protagonist—it would be weird to think of Claire or Andrew as the sole protagonist of the whole movie. While all five of them have key speeches and pieces of dialogue, they are journeying to something that they all share; it's not any one student's specific property.
Without other characters to share their realizations with, no one in The Breakfast Club would've broken out of their set ideas about each other (except maybe a reflective introvert like Allison). When Claire tells Brian that he doesn't understand the kind of pressure that she and Andrew face from their popular friends, Brian explains that he does understand pressure, and tells the sad story about how he wanted to kill himself after failing shop.
So they both come to understand that they're experiencing this unbearable pressure in different ways—it's something that happens in dialogue, between them. It's not just one character's insight. "The Breakfast Club" itself is the hero of the story—one five-headed protagonist. Its goal is to triumph over its own incorrect assumptions and preconceptions and realize its own united identity.