Gate Guardian

The Gate Guardian appears in the episode "Death in Bloom." He does not allow Finn and Jake into the Land of the Dead since they are alive. However, they distract him long enough to walk in the gate behind him. He then yells for them to come back, but they were already too far gone to care. He usually asks for how somebody died when they get to the gates of the Land of the Dead.

Appearance
The Gate Guardian appears to look like a skeletal pterodactyl of some sort with one large eye and large purple wings. Curiously, there is a ladder perched up on his hip bone. It is unknown if it is just sitting there, or if it is a part of him. He also has small strings of what appears to be slime dripping from a few of his bones.

Trivia

 * The Gate Guardian may be based off of Cerberus: a three-headed dog that guards the gates of Hades.
 * In the storyboard for Death in Bloom, the Gate Guardian is fleshy, not skeletal, and does not have wings.