I've got toddlers visiting right now, and it's given me a great chance to think about the dramatic unities and Aristotle. Let me explain.
Like all toddlers, these two go from happy, curious, and delightful to screaming banshee devil spawn faster than you can say bath time. We were playing a dinosaur game: adding -osaur to everything. Scriptwrangler-osaur is going to get Dante-osaur with the help of... blanket-osaur! And then the little girl hit her brother. And the biting started. So Scriptwrangler-osaur let himself get killed by Dante-osaur, and it was time for a new game. More wailing. But we moved on.
Next day, we play the same game. As the bad stuff starts coming out, Scriptwrangler-osaur takes a dive. Time for a new game. There's wailing, but less so.
Third day, same game. As things are starting to get out of hand, I fall to the ground. Is he dead? Silence. I peeked. The little girl gave me a hug. They knew what this means, and they backed off. They learned the pattern. All right, maybe I just got lucky. But there's a point here.
There's something very special about the number three. If we see something once, it's an event. If we see it twice, it's a tendency. If we see it three times, it become a pattern: something that can be relied upon. Movie viewers rely on it. And writers rely on it. It helps create a unity, a cohesiveness, to your story which can be extremely helpful.
Humans are pattern-recognition machines. We are hard-wired for it. More than that, we love to do it. That's a large part of why we love stories. We love to find the one thing that is different. Building patterns and parallels into your script can communicate more than pages of dialogue. Take a look at the exercise in the posting below (Props Manager: The Game). We took a scene, and then swapped out props to see how that changed the meaning and the feel of the scene.
Now change it up a bit. Take your scenes, and try to lay out three variations in a sequence. Try to build a story. Try to show development. For example: three scenes with (much of) the same dialogue.
Say you've got an elderly man sitting next to his wheelchair-bound wife in the park.
Next, he's walking with a cane in the park, talking to his daughter. Same dialogue, different character.
Third he's by himself, in a wheelchair. He talks to himself.
That's a rather sad story. But you can use patterns to achieve any dramatic goal, from humor, to relationship development, to plot development. You name it.
A geeky young man tries to convince his overbearing mother to go to the comic book convention with him. She tells him to grow up.
The same guy asks a fashion model on a date... to the comic book convention. He repeats the same lines. She rejects him mercilessly.
The same geeky guy rides the bus alone. Pulls up to the comic book convention. Meets eyes with a geeky girl as they both get off. She repeats his line to him. He smiles.
Ta da. Love story.
Try it. Play props manager. See what happens.