Right?? Lol I first discovered the show years ago and literally never gave a second thought to the lyrics, if anything I thought the "one by one they all just fade away" line was in reference to the idea of *leaving* rather than staying--hence why I probably thought it was more upbeat than not. However, now knowing how Dan Harmon's style is, it's not surprising at all. It would actually be MORE unsettling to me if the song was, in fact, actually upbeat.