In the modern age a persona is indistinguishable from a person. They magnify what is within us, and what we bring out within others. It is a shared delusion powerful enough to claim a life of its own.
Over the course of my time as an operative I have developed relationships with several individuals in an effort to diversify the skills available to me. Some in my profession call them assets, I prefer to think of them as associates.
"Impatient as well as stupid, some virtuous whip you are." Snap tilts her head to the side with a smile as her drumming fingers increase in tempo. "I assure you that my patience is vast." The man stops in his tracks stare Snap down, her expression remains unchanged. "Vast, not infinite. I am but a human so I am sure something could cause me to break my vows." Hastily he resumes filling the order. As Snap walks out the door with the goods the shopkeep grabs your arm. "That is a monster chained by monks robes, I have stared down raging barbarians and never seen such hate in their eyes."
Pirate captain of the legendary Red Dawn, Amanita lives to strike fear into the hearts of others. Her S&M cult and smuggling operations often hide behind the guise of bakeries, but there is a reason for all that a person does.
NPCs can be so dry and bland when they come up and you aren't prepared for them. Other NPCs often times only have the stats rolled up and their personalities are neglected. That is where a list of simple characteristics can come in handy and you can stereotype the NPC and at least give them some kind of quirk that defines them a little better. Nobody may remember the innkeeper at that one city, but they may very well remember the innkeeper that picked his nose right before he gave the players their change. Just some little things to define the NPCs and make them more real. Some can be used by players as well to spice up their character a little.
A demon who isn't some hideous creature bent on consuming souls, bu is, in fact, a likable chap who enjoys having pleasant chats with people - trying to talk them into becoming his servants.