As an exercise in exploring my principle -- Character = Function -- let's take a look at each of these primary and secondary characters in Trainwreck: Amy (protagonist): It's her story, her journey, her narrative point of view, plus she's the character who goes through the most significant psychological and emotional metamorphosis. Kim (sister): I look at Kim as a Mentor, her life and lifestyle an example of Amy thinks she does NOT want - at the beginning - but over time comes to understand is not an example of being trapped, but instead if embraced as an act of volition, represents a legitimate choice. A bridge for Amy to come around to the idea of being involved in a sustained monogamous relationship. Gordon (father): Trickster. He gave the girls life. Supported them. But laid on them, especially Amy, the idea that monogamy simply doesn't work, based on his own infidelities. His Trickster behavior continues via the problems Gordon gets into at the old folks home. It's even exhibited at the funeral where Amy admits the guy was a fuck-up, yet still worthy of love. Symbolically his death contributes to Amy being able to move away from Gordon's awful advice about monogamy. Steven (current boyfriend): A necessary starting point character to demonstrate the 'wrong' boyfriend and how off Amy's POV is re romance. Nikki (workplace best friend): Ally and confidante. A Mentor figure in the sense she supports Amy's old way of being, but representing - ultimately - the wrong way of thinking. Dianna (boss): Mentor (Negative). If Steven represents a Negative Attractor, related to Amy's love life, Dianna represents what would be in store for Amy if she were to throw herself into career at the expense of her emotional development. Donald (young intern): Attractor (Negative). Basically two things: (1) To reinforce for Amy the fallacy of a life focused on sleeping around. She needs this reminder late in the game. (2) His youth drives home how infantile her original way of being was. Aaron (prospective boyfriend): Attractor. As much as she struggles with growing up, Aaron is the ideal match, long-suffering, patient, stable, yet fun-loving. Lebron (Aaron’s friend / NBA star): Mentor, mostly in relation to Aaron, but helpful indirectly in steering Aaron into and through the relationship with Amy. Big payoff: The intervention. Tom (Kim’s husband): Amy typecasts him as a boring husband, but over time comes to see him in a different light. Allister (Tom’s son): See above, only substitute "child" for "husband" and "weird" for "boring". Noah (resident panhandler): Trickster. Basically a Greek chorus figure commenting on Amy's behavior, probably the voice of her own doubts and insecurities about her partying behavior. Every character has a function in this story. That's just the way it is in movies. No room for extraneous characters who do not support the movement of the plot and the Protagonist's journey.