What scares Charlie?
Aging, loneliness, losing your mind and falling apart. That's according to a good interview with The Atlantic.
Kaufman: I’ve found things over the years where I said, “Oh my God,” called my agent to see if it was available, and invariably got cold feet. But I committed to [this one], and Iain Reid and I developed an over-the-phone friendship. That initial contact with him, before the buyer’s remorse kicked in, made it happen.
[...]
Sims: I want to talk about the musical Oklahoma. When did you decide to incorporate that into the action?
Kaufman: Once I replaced the interstitial sections with this night janitor, I was thinking of things that could exist in the school while he’s working, and I thought of a play rehearsal. I actually was in a production of Oklahoma when I was in junior high school. I know the play very well, and there are some perfect parallels, particularly with the character of Jud and the dream ballet. It was challenging to get Rodgers and Hammerstein’s estate to give us the rights to use those songs. But they did ultimately.
[...]
Sims: It’s a horror movie—all the films you’ve directed brush against that genre, but the horror is quite mundane. It’s time, it’s death, it’s other people.
Kaufman: When I come up against the genre directly, which I did with Iain’s book, I can’t do it. I’m not going to have a cat jump out; I’m not going to have [scary] music or editing unless I can subvert them into something else. I bring it back to the things you said I find scary. Which are aging, loneliness, losing your mind, and falling apart. (Source)