In most stories, the main character is the hero who changes. However, in rare cases, the main character is actually the mentor who doesn’t change but helps someone else change instead. Two movies that demonstrate this structure is “WALL-E” and “Marshall.”
In “WALL-E,” the hero is a trash compacting robot who just wants to find love. Yet throughout his existence, he doesn’t change. He simply wants to find someone to love. The character who does change is Eve. At first, Eve is just doing her job and doesn’t care about emotions. Gradually through her contact with WALL-E, she learns to share emotions by first becoming WALL-E’s friend. Then she becomes WALL-E’s ally in helping save the plant. Finally she realizes how much WALL-E cares for her that she finally falls in love with him.
In the meantime, WALL-E goes around helping everyone he meets. He helps a human couple meet and fall in love, he helps the starship captain learn to literally stand on his own two feet, he helps an army of rogue robots stand up for themselves as well, and he teaches other robots to not just be mindless automatons but to care. WALL-E is a mentor figure because he helps others change around him.
“Marshall” is the story about a black lawyer named Thurgood Marshall who protected the legal rights of blacks in the 40’s. Through the story, Marshall doesn’t change, but he helps a fellow lawyer change. This fellow lawyer is Jewish and focuses on trivial insurance cases where he uses technicalities to win. When this Jewish lawyer is forced to work with Marshall, he’s forced to stand up for the rights of the oppressed and learn how to become a trial lawyer. Through Marshall’s tutoring, this Jewish lawyer becomes competent in his own right and wins a major case to protect a black man accused of rape.
Marshall may be the main character but he doesn’t change. From start to finish he’s always fighting for justice for blacks. The Jewish lawyer is the one who changes through contact with Marshall.
So when writing your own screenplay, look first at how your main character can be the hero and change. If that doesn’t work for your story, look at turning your main character into a mentor and changing the lives of someone else instead. In every story, someone has to change. Usually it’s the main character but sometimes it can be a secondary character as well.