Board Thread:Questions and Answers/@comment-27327020-20160404174206/@comment-13682699-20170606053334

Riiingo wrote: The fact that they are in the game even though he should technically not exist yet appearing at random points in the game says that the fact he doesnt exist isn't too reliable. Its like I said though. TECHNICALLY he doesn't exist. By all standards of measurement for the Undertale universe, Gaster does not exist. HOWEVER, we as players are outside this Universe and we are able to see/manipulate events from an outside perspective. The only others who share this perspective are characters who are specifically designed to have a slightly different perspective and knowledge of the world they live in, like his followers(who also only briefly appear) and, most notably, Sans.