Reincarnation

Reincarnation is  concept that the soul  or spirt, after biological death,  begins a new life in a new body that may be human, animal or spiritual. In Adventure Time, this is one of the many outcomes that await the people of Ooo after death.

Mechanics
Not much is currently known about how reincarnation works, as only one character, Finn, is confirmed to have past lives. What is known, is that people who have been reincarnated may remember their past lives through hypnosis.

Trivia

 * Reincarnation is a common belief of various ancient and modern religions such as Spiritism, Theosophy, and Eckankar and is found in many tribal societies around the world, in places such as Siberia, West Africa, North America, and Australia.