He appeared in the episode "Furniture & Meat" where audiences discover that he was hidden in Finn and Jake's gold stash. It is then commanded to "chill" and does so throughout the episode.
He was referred to as "the" Ancient Psychic Tandem War Elephant whenever he was mentioned, meaning he is or may be the only one of his kind.
In "Something Big," the elephant is summoned by Finn and Jake to save the Candy Kingdom from Maja and Darren, who recognizes the elephant as "Eli" (pronounced "Ellie"). After helping Finn and Jake destroy Darren and zapping Maja (which hurls her into a tree, where she hits her head and goes into a coma), the elephant is left at odds as to what to do with itself, and is disappointed by Finn's attempt to set it free, as it feels a need to follow psychic commands as a war machine. After traveling about Ooo and reading the thoughts of such beings as an ant, a mama bird and the sun (which gives it advice to take control of its own destiny), it retrieves the comatose Maja and psychically explains to her that it will watch over her until she gets better, much to Maja's annoyance. It is also mentioned by Finn that the elephant had resided in the Tree Fort's basement since the events of "The Limit."