This song is based off of a creepypasta with the same name, Mr. Widemouth. If you haven't read it, I suggest checking it out (I'll link it below). Summary of the story, when a kid was really young, he got pretty sick, and had to stay at home. And during that time, he made a friend, a friend who stayed in his room and hid whenever the kid's parents were around. A friend that wasn't exactly human. A friend who just wanted to have some fun, but some of the fun he suggested sounded a bit dangerous...