It doesn’t have to be anything bad btw
My secret is that I know I’m actually the only real human, and everybody else are aliens posing as humans to study my behavior. That’s why I purposefully make random decisions and actions from time to time, to throw them off.
I still have to figure out if I’m the last human alive, if every remaining human is being studied like me, or if there is a real human society somewhere.
I suppose we should tell them now.
You’re not actual a “real human.” You’re an alien just like us, but we convinced you that you were human so we could study “human behavior”. One behavior we’ve identified is paranoia.
Reminds me so much of a particular Philip K. Dick story. A solider’s tour in Korea is over and returning home he notices that everything is fake. Artificial sweetener, instant coffee, faux leather shoes, hair styles, etc. He gets the idea that the aliens took over the US and setup a few fake burbs for the soldiers returning home, to isolate them and eventually pick them off one by one.