Holy shit. I know this might be old news to some of you, but I just learned that the show Adventure Time is actually set in a post-apocalyptic future in which Finn is the last un-mutated human on earth. The “Great Mushroom War” refers to nuclear war. These pictures definitely confirm foul play…
Also, the Ice King was once a human named Simon Petrikov. He studied artifacts and came across a crown that gave him visions, mutated his body, and eventually deteriorated his entire mental condition. Check this video.
So what I’m getting from all this is that Adventure time is really about a survivor of a nuclear war (who is possibly suffering from a mental condition as well) trying to find fun and adventure in the world with his mutated dog. All the while, the main antagonist is just trying to find a way to get his “princess” and happiness back, but can’t because of his condition.