If you haven't dabbled much in RPGs (either pen and paper or the video game kind), you might not be familiar with the difference between NPCs and PCs. If that's the case, I encourage you to click those links now and go educate yourself. Are we on the same page? Good.
I assure you that these are not merely conventions invented for gaming. These designations are applicable in real life. There are NPCs among us. They may pass immediate inspection, but I guarantee you that you interacted with at least one today. And probably more than one. Not only am I sure that they exist, I'm pretty convinced that they outnumber us.
I'm not saying that the world revolves around me and exists purely for my entertainment. This is not the Truman Show. There are certainly other PCs out there. But it seems that we're part of some sort of sinister game where we have to wade through hordes of NPCs to find each other. And what happens if we don't? Maybe there is a Rapture, and all these NPCs are actually robots, and when "the time comes" all the robots are going to explode and you had better hope you surrounded yourself with PCs and not NPCs.
I may sound crazy, but I'm only half kidding. Sometimes while I'm talking to someone I'm wondering to myself if they're, you know, real. And then I find myself poking and prodding them in interesting ways (verbally, not physically), just to see their reaction and make sure that they're not a soulless robot. These robots have many canned responses to trick you, but you just might catch them unawares and see just how shallow they are.
They might not be robots. Maybe they're all extremely diluted clones (which can also be filed under "Things that always turn evil") that are placed around us to "fill out the place."
Maybe it's just some sort of chemical imbalance. Some people get ADHD, others are stuck being NPCs. In which case it's maybe curable? No, don't sympathize with them! When you know you've found one just run away. Trust me.
Oh, and for those of you that can't make heads or tails of the title of this post, just consult your local reference of geeky gaming acronyms. And forgive me for putting you through that.