I have been trying to figure out what show this story came from for the last few years.
A scientist is on the brink of creating a fully realized artificial world for the first time, complete with its own inhabitants. He explains to an incredulous colleague who thinks that the inhabitants will realize that they are in a simulation that since these people never alter their daily routines, they will never discover the edges of their world, and thus will not learn the true nature of their reality. The episode ends with the scientist being questioned as to whether he has ever adjusted his own daily routine in an unexpected way, and his realization that he has not. He drives down a road out of town in a way that he has never gone before, and suddenly discovers that the edge of town disappears into a grid of unformed nothingness, and he realizes that he is in fact living inside a simulation himself.
This is the earliest representation of simulation theory that I remember seeing on TV - but I have no idea what show it was from. I have a feeling it may have been The Outer Limits, or The Twilight Zone, but having read all of the episode synopses of both shows, none of them seem to be this story. Has anybody here ever heard of this?