Setting ?

The show is set in a fictional continent called the "Land of Ooo" and, although it is not explicitly stated in the show, it takes place in a post-apocalyptic world some time after a nuclear war called the "Great Mushroom War." According to Ward, the show takes place "after the bombs have fallen and magic has come back into the world". During a presentation at the Toronto Comics and Arts Festival, Ward said that this will likely never be directly addressed in the series.
In the holiday special "Holly Jolly Secrets", Finn and Jake discover a few secret VHS tapes by the Ice King. The last tape shows Ice King as a human. In the video, Ice King says his name is Simon Petrikov and he was studying to be an antiquarian of ancient artifacts. In his secret tape, he explains he purchased his golden crown from an old dock worker in northern Scandinavia, a reference that apparently confirms that the "Land of Ooo" is actually a part of Earth. Also, in "Beautopia," a character by the name of Susan Strong is implied to be human as well, although she belongs to a strange fish headed, animal hatted mutant tribe.
In the episode "The Real You", when Finn wears the Glasses of Nerdicon, planet Earth can be briefly seen from space, with a large chunk missing from it. Later it is shown in the episode "Five Short Graybles," which initially shows the storyteller with a rotating holographic globe with a portion missing, where the North American continent would be.
Such apocalyptic setting is not implemented in the Random! Cartoons short.




credits : http://en.wikipedia.org/wiki/Adventure_Time#Inspiration