Mushroom War

The Mushroom War was an apocalyptic event, which happened around 1000 years before the adventures of Jake the dog and Finn the human. There is evidence throughout the TV-show, that this was a nuclear war, which destroyed most of the life as we know it on planet earth. As a result, this created an enormous crater in or on which the new Land of Ooo formed.

Survivors

 * Marceline
 * Hunson Abadeer - although he probably spent his time in the Nightosphere
 * Simon Petrikov