Not sure if anyone out there has ever converted prose to film. I've done it. A feature length film is actually, in prose, roughly the plot length of a short story. It's why folks complain about novel conversions so much.
I think it was Neil Gaiman who said he could only write really dark main characters in short stories. He just couldn't stand spending an entire novel with someone like that. So, if you think of the crazy, unforgettable characters we've met in film, some we love (the kids from Narnia, Aragorn as Strider) and the ones we don't love so much (Hannibal Lector) think of them in terms of a short story.
I find myself reeling back into calmer waters, character-wise, for novels. In short stories, I tend to let myself go. Great short stories (arguably, great stories, period) have memorable characters. But I think short stories have extra leeway. Sometimes I find in my slushpile that the characters just aren't enough, somehow. Some of this rests on motivation: strong motivation makes for strong actions which leads to strong characters. But I look for quirky characters, too; characters that push the boundaries of who they are.
I recently watched Transformers, which made for great character study. The writers took stock characters -- the out-of-touch cop, the pretty girl with a secret past, the mother trying to connect with her teenaged son, the "secret agent" who means well but isn't above throwing his weight around, the heroic soldiers -- and they pushed the boundaries of what it meant to be that character. To steal a cliched line from the film, at which the writers poke fun via dialogue, there was "more than meets the eye" to every character. They shoved the boundaries, down to the car salesman played by Bernie Mac. ("Gentlemen, Bobby Bolivia. Like the country except without the runs." ) Bobby was a typical used car salesman, but so obviously more, shouting at his deaf Mammy and making snide comments about cheap-ass fathers. When Bobby left the screen I was sorry to see him go.
Make your readers sorry to see your character go, and you'll find your story in our pages.