Humans

Humans are a critically endangered species in the Land of Ooo. It is hinted that they were driven to near extinction roughly a thousand years before the events of Adventure Time during an event called the Mushroom War, a global thermonuclear war.

Current Status
Many residents of the Ooo are under the impression that humans no longer exist as demonstrated by Bob and Ethel Rainicorn in "Her Parents." Due to their rarity, many characters marvel at Finn's humanity, such as Princess Bubblegum in the episode "Susan Strong."

There are several other beings that resemble humans in the Land of Ooo, such as Penny, Phil or the Old Man Henchman. Despite their resemblances, most of these beings are not recognized by other characters to be humans. According to the show's writers, these characters should be referred to as humanoids or mutants. Some of these beings, however, were actually humans in the past, which includes Ice King, Business Men, and Moe. The old ladies scattered around Ooo from "The Enchiridion!" and "Be Sweet" are very human like but are actually a species of old ladies, as revealed in "Thanks for the Crabapples, Guiseppe".

Finn was the only confirmed human until "Betty" when Simon accidentally brings Betty into the future, and in "Billy's Bucket List " when Finn's father, is confirmed be alive. It is confirmed in "Dark Purple" that Susan Strong is indeed human. However, she seems to have cybernetic implants in her head, implying that she is not entirely human. Later, in "You Forgot Your Floaties", Betty became a Wizard by using Magic Man's powers, so she is now no longer fully human. Martin is shown to become a Cosmic Entity in the events of "The Comet".

In "Everything's Stays", a tribe of humans were seen departing the continent of Ooo on a patched-up pre-war ship. It is unknown if this tribe still exists, or if they even managed to leave Ooo. It is probable that these humans are the hyoomans before their intellectual regression, and possibly before their mutation, due to the similar attire. The young girl in this episode also strongly resembles a young version Susan Strong.

Known humans

 * Finn (possible Cosmic Entity)
 * Fionna (fictional)
 * Flynn (Comic only)
 * Human tribes on other continents like Two Bread Tom (status unkown)

Deceased humans

 * Abe Lincoln (Cosmic Entity as revealed in "Orgalorg")
 * Commander and Private (Animated Movie)
 * Marceline's mom (confirmed at Wondercon 2013)
 * Most humans before the Mushroom War

Known former humans

 * Simon Petrikov (now a wizard)
 * Betty Grof (now a wizard)
 * Moe (now a cyborg)
 * Susan Strong (cybernetic implants placed in her during an unknown time make her a cyborg of sorts)
 * Randall N. Byron (now computer software; Comic only)
 * Business Men (now mutants/zombies)
 * Martin (now a cosmic entity)

Hybrid humans

 * Marceline (formerly a Human/Demon hybrid, currently a Vampire/Demon)
 * Jay & Bonnie (Human/Pillow hybrid)
 * Stormo (by DNA)
 * Adventure Tim (Human/Dog hybrid; Comic only)
 * Susan Strong (mostly Human, but has an unknown amount of cybernetic implants placed in her during an unknown time)

Humans from the Farmworld timeline

 * Finn Mertens
 * Finn's mom
 * Finn's Dad
 * Finn's Baby Brother
 * Choose Bruce
 * Destiny Gang
 * Big Destiny
 * Trami
 * Tromo
 * Unnamed Destiny Gang Members