|One of these four (car included) will not survive the day.|
Howard Suber has taught innumerable courses at UCLA. He is a gifted teacher of screenwriting, and I highly recommend his book, The Power of Film. In it, Suber writes, "There are two basic kinds of change in storytelling: of circumstances and of character." In changes of circumstances, he goes on to say, "the circumstances of the central character change, but by the film's end the characters are still essentially who they were in the beginning."
In changes of character, he says, "the central characters... are not only in greatly changed circumstances by the end of the film – they are not who they were at the beginning" and "Such changes of character are even more important than the changes in circumstances."
Ferris undergoes a change of circumstances. His grumpy principal, Ed Rooney, takes it upon himself to catch Ferris in the act of skipping school. And, for the first time, he does. It's a position in which Ferris has never before been. His own sister comments that everything works out for him. But on this day, it doesn't. Ferris is stuck in a situation that he can't escape on his own. The look in his eyes (and the script) when Rooney finally confronts him tells us so:
But of all the characters in the film, Cameron has the clearest change of character, the greatest barrier to overcome, and is, in my opinion, the most interesting character in the story. Where does he start? He won't even climb out of bed until Ferris annoys him enough to leave his own room. He says, "I can't handle anything: school, parents, the future." Where does he end up? Killing his father's prized car. It might be Ferris's day off, but it's Cameron who grows up.
How do you inject such a powerful emotional arc into your own stories?
In The Godfather, Michael Corleone goes from, "That's my family, Kay. It's not me" to "Just lie here, Pop. I'll take care of you, now. I'm with you now. I'm with you."
In Finding Nemo, Marlin goes from "You think you can do these things, but you can't, Nemo!" to "You're right. I know you can."
In The Shawshank Redemption, Red goes from, "Hope is a dangerous thing. Hope can drive a man insane" to "I hope."
In Up, Carl goes from, "Stay away from our mailbox! I don't want you to touch it!" to "You know, it's just a house."
These are lines, of course, and they're not a bad place to start. But when it comes to really plotting out character arc, better still would be to find defining actions:
In The Graduate, Benjamin floats directionless in a swimming pool. In the end, he steals Elaine from her own wedding.
In As Good as it Gets, Melvin Udall goes from shoving a dog down a garbage chute to demonstrating care and compassion for said dog.
In Jurassic Park, Dr. Alan Grant goes from threatening a child to saving children.
In Ferris Bueller, Cameron goes from bedridden to car-killer.
Cameron starts in Egypt. He makes it to his Promised Land, and it's better than anything for which Ferris could've prepared him. If you're not sure what to do with your character, then having a clear idea as to where they start and where they end is a great way to begin the process.