A title drop is when a character in a movie says the title of the movie they're in. Here's a large-scale analysis of 73,921 movies from the last 80 years on how often, when and maybe even why that happens.
Whenever you are dealing with large datasets like this it is really easy to have your rules generate false positives or false negatives. You would almost have to go through and verify each movie to get 100% accurate.