"The greatest ending line in movies" just popped out

In this interview, Billy Wilder discusses his writing partner I.A.L. Diamond and how they came up with the final line of "Some Like it Hot."

We had a great deal of trust in each other. But sometimes with writing you just can’t tell, especially if you’re writing under pressure. Diamond and I were writing the final scene of Some Like It Hot the week before we shot it. We’d come to the situation where Lemmon tries to convince Joe B. Brown that he cannot marry him.

“Why?” Brown says.

“Because I smoke!”

“That’s all right as far as I’m concerned.”

Finally Lemmon rips his wig off and yells at him, “I’m a boy! Because I’m a boy!”

Diamond and I were in our room working together, waiting for the next line—Joe B. Brown’s response, the final line, the curtain line of the film—to come to us. Then I heard Diamond say, “Nobody’s perfect.” I thought about it and I said, Well, let’s put in “Nobody’s perfect” for now. But only for the time being. We have a whole week to think about it. We thought about it all week. Neither of us could come up with anything better, so we shot that line, still not entirely satisfied. When we screened the movie, that line got one of the biggest laughs I’ve ever heard in the theater. But we just hadn’t trusted it when we wrote it; we just didn’t see it. “Nobody’s perfect.” The line had come too easily, just popped out.

The easy stuff that just pops out seems like it's not worth as much. But sometimes it's the effortless stuff that's actually gold. And maybe it just seemed easy but your subconscious was grinding on it for a while.

Btw, the "let's put it in for now" into "that's actually really good" turn of that story reminds me of how John convinced Paul to keep an odd lyric in "Hey Jude."

I finished it all up in Cavendish and I was in the music room upstairs when John and Yoko came to visit and they were right behind me over my right shoulder, standing up, listening to it as I played it to them, and when I got to the line, 'The movement you need is on your shoulder,' I looked over my shoulder and I said, 'I'll change that, it's a bit crummy. I was just blocking it out,' and John said, 'You won't, you know. That's the best line in it!' That's collaboration. When someone's that firm about a line that you're going to junk, and he said, 'No, keep it in.' So of course you love that line twice as much because it's a little stray, it's a little mutt that you were about to put down and it was reprieved and so it's more beautiful than ever. I love those words now...

Time lends a little credence to things. You can't knock it, it just did so well. But when I'm singing it, that is when I think of John, when I hear myself singing that line; it's an emotional point in the song.