This is for me, so I remember. From a Joss Whedon interview, here.
I’ll have an idea, and then I’ll start to think about what’s behind that, and what would be the big emotional moment, what would be the catch, what would be the thing I’d love to see. It’s usually easier in a situation with a known quantity. For example, Wonder Woman. Like, how do you introduce Wonder Woman? “Oh, that’s cool.” I did Aliens 4. When I first wrote it, it was a 30-page treatment that was completely different from what they shot. It didn’t have Ripley in it. Somebody just said, “We’re interested. Would you write a treatment on spec?” I was like, “It’s Alien. Are you kidding? I’ll carve one on my forehead.” That hurt, so I stopped and used paper. [Laughs.] Paper has worked out great for me since, really. But, I thought to myself, “Okay, I’ve seen three Alien movies. Alien is one of the most important franchises in my mythic history. What haven’t I seen? What are the moments that I go, ‘Okay, that’s new, that’s worse, that’s good, give me that’?”
It’s easy doing that with a script for a TV show. You can feel the characters, you can get to the emotional moment. With a new thing, it’s still part of the process. The most obvious example, and I’ve used it before, is Buffy in the alley. I really thought about it: [Trailer narration voice.] “It’s a bad town to be in, especially at night.” There’s the girl in the alley. “Especially if you’re alone.” And then the monster attacks her and she kills it. “And especially if you’re a vampire.” It was that turnaround, which I hadn’t seen, and which has obviously been seen a million times now, but this was 20 years ago. I wrote that, and it’s in the actual movie. They didn’t use it for the trailer, and the scene isn’t shot exactly how I imagined it. But when I’m thinking of a trailer moment, I’m not just thinking of how I can grab people. That’s my whole philosophy. My entire career is in that trailer moment: The emotional highs of the movie, and the thing you haven’t seen, and the thing you’re longing for. They should all be connected.