And sometimes things can be lurking in the back of your brain, though the Hunger Games movie seems a bit recent for that.

I was guilty of it once, myself. I wrote a fanfic years ago that had a character throw an apple at a person, bean him in the nose, then say, "Waste of a good apple." It wasn't until months later that a light bulb went off and I remembered that exact same thing happened in Lord of the Rings, and I had completely forgotten that scene. I went back and added an apology and explanation, but boy was I embarrassed.