Super Eyepatch Wolf made an Undertale Review where he goes nearly insane because of the size and depth of the fandom:
Undertale is probably the most meta thing that any human being has ever produced. It's hard to judge the game and its place in the world since it's not just a game, it's a combination of game, nostalgia, social media, societal trends, and the kind of explosive creativity that only the most prosperous and technologically advanced era of in all of human history could produce. It makes the Weimar Republic look like a knitting circle.
If I weren't familiar with anime, Earthbound, and early internet culture, I wonder how much I'd really understand this game besides "Ha Ha, Cute characters." The pacifism also turns me off since I don't think you should be teaching children the message of "You should always try to negotiate with something that's trying to kill you."