Humans

Humans are a critically endangered species in the post-apocalyptic setting of Adventure Time. It is suspected that Finn was the last human on Earth. Many characters have marveled at Finn's humanity, like Princess Bubblegum in the episode "Susan Strong." Bob Rainicorn even went as far as to say that he and his wife Ethel Rainicorn believed humans to be extinct. The scarce Human population in the Land of Ooo can probably be attributed to the Mushroom War, a war that took place some time before the present story line and is thought to have involved the excessive use of nuclear arms. Another possible cause for the scarce number of humans might be that the inhabitants of Ooo devoured the humans, as species such as Skeletons and Rainicorns have a desire for their flesh.

Note that there are other beings in Ooo (such as Pajama Ninja or Old Man Henchman) that seem to resemble humans. However, Finn and the other characters do not recognize them as humans. According to the show's writers, these characters should be referred to as "humanoids" or mutants.

Known humans

 * FinnCAP12.png
 * Fionna (fictional)

Deceased humans

 * The Commander and Private actors from the movie "Heat Signature."
 * Abraham Lincoln
 * Betty (Unknown)

Possible Humans

 * Susan Strong
 * Old Man
 * Ninjas

Hybrid Humans

 * Princess Bubblegum

Known Former humans

 * Ice King (formerly Simon Petrikov)

Possible former humans
Undead creatures such as skeletons, and ghosts could have formerly been humans, although they could also be the remains of humanoids or other creatures.
 * Hunson Abadeer
 * Marceline
 * Wendy
 * Georgy
 * Booboo
 * Skeleton
 * Skeleton Baby
 * Skeleton Mom
 * Skeleton Army
 * Skeleton Princess
 * Boyfriend & Girlfriend Skeletons
 * Skeletal Guards
 * Business Men
 * Princess Beautiful
 * King of Thieves
 * Marshall Lee (fictional)
 * Ice Queen (fictional)