Sometimes, in our zeal not to inflict too many characters on our readers, we forget that characters-as-scenery still have a role to play.
The image above is one of my real-life non-player characters, as rendered by a simple MidJourney AI image prompt [MidJourney has some challenges rendering animals….]. He's a shrew, and his name is Samson.
Let me explain…
We currently live in an 1812 stone and log cabin at the the top of a hollow embedded in the rise of the Allegheny plateau, part of a large bit of land we bought for hunting & vacation back in the '80s. (More details here and here and elsewhere.) The original settler's cabin had a single main room downstairs built into the hillside with a fireplace for living/cooking, and three rooms above for sleeping. A small plumbing/furnace extension in the 20th c. added a cellar/pantry below and another bedroom above.
Old buildings like this are, shall we say, semi-permeable to the local wildlife. Squirrels roll walnuts between the walls, snakes take advantage of knotholes in the logs, and mice dare our traps to spend the winter. Mostly they don't make their presence obvious, and we indulge in a fair amount of live and let live (undermined by occasionally disapproving cats who take matters into their own paws).
Recently we've added a member to our volunteer menagerie. A floorboard in the main room downstairs has broken at the corner and exposed a matchbook-sized hole to whatever ground-level original dirt or flooring surface lies below. And, so, a shrew has come to join us.
Now, a shrew has got about the fastest metabolism of any mammal. You never see one standing still, just blurring by at high speed, and since they're the size of a mouse or smaller, if you blink you'll miss them. We're sure of our identification, because the first one ran through the main room from the fireplace corner to the dogs' water dish in the adjacent cellar. We once carelessly left the water level too low for her to get out, and she drowned (providing the evidence). We lamented the unintended death (and named her Ophelia), but soon she was replaced by a successor who is providing us with a great deal of amusement.
You see, this one has taken up some form of construction. He zooms from the floorboard hole to the back of our cheap modern electric stove and proceeds to make an astonishing amount of noise involving metal and scrabbling (and jackhammers and god knows what) — this, despite the oven still being in use periodically, to no apparent effect.
And now comes the point of this post… We want to know what this shrew is doing. We've invented a rationale (he's building bookcases under the oven to hold his comic collection – hence the image above) and we've given him a name (Samson) in recognition of his prodigious activities.
We had to do that — this is a critter with agency whom we encounter on a regular basis. We had to create a story for him. It's what people do. It's beside the point whether the story is true or not.
Well, your fictional POV characters would do the same with the people and other critters in their environment, wouldn't they? That's what struck me; unlike some of my fantasy worlds with limited numbers of onstage people, my current WIP is set in a faux-regency urban environment, and that means that my characters would naturally see all sorts of people all the time — the beggar on a corner, the tailor's assistant sweeping his master's steps every morning, the gentleman who tips his hat to you because you have come to recognize each other on your daily walks, the mangy cat who shows up looking for a handout. None of these are named characters, and none will provide a POV, but that doesn't mean they shouldn't be there, and that your real POV characters don't notice and speculate about them casually, the way we all do. Add them to your fictional world's environment and make it seem more like real life (and less of a vacuum).