What is the best example of attention to detail in a movie, something that 99% of the audience won'…

What is the best example of attention to detail in a movie, something that 99% of the audience won't notice but enhances the movie and makes the experience better for those that do notice?

A short hit of movie/TV chaos for people with strong opinions.

2 quick answers. Which take would start the biggest argument?

#fandom #tvshows #popculture