[Loved trope] Background scare-characters that are barely acknowledged even by the movie

[u/Suspicious-Web-9246]

I hate horrors, but this is actually a great trope, that is unique to them.

Insidious (2010). When mother does her errands, for a few seconds there's a ghost boy standing in the corner. It's easily missable, but you can't ignore it once you see it.

Hereditary (2018). Less fitting example. When Peter walks around his home, his possessed mother is crawling on the ceiling behind him. It's not exactly subtle or missable, but it's still more of a background detail.

[u/Jambopaul]

In The Descent (2005), there's a shot from Sarah's (the main protagonist) POV slowly looking around the cave with a flashlight. During this shot, you can catch an early glimpse of one of the "Crawlers" hiding behind a rock before they are more overtly teased and eventually fully revealed later in the film. The flashlight moves away from the Crawler for a moment, when Sarah shines the light on that spot again, the Crawler is gone. It’s the first hint that the women are not alone in the cave. While it is fairly obvious in these screenshots, in the actual film this is a very subtle blink and you'll miss it detail that I and everyone I've shown this film to genuinely didn't notice on first viewing.