Sloane is Ferris' girlfriend, and she didn't ditch school, so they have to break her out of prison. The prison guard is well played by Del Close. Second step is to get Cameron to steal his father's car, a cherry apple-red 1961 Ferrarri convertible, of which only one hundred were made. Even Cameron's father doesn't drive it. It has less than two hundred miles on it.
Third step is to go out and have fun after breaking all the rules.
Part of making this movie was John Hughes' desire to show off Chicago, where he grew up. You can laugh at it, sing along with it, and almost believe the silliness in every scene. It has a cartoon quality that puts you into the story. But it doesn't dwell on the message and it doesn't dig too deeply. That ends up being both its success and its failure, but I count it as more of a success.