The season follows the adventures of Finn (a human boy) and his best friend and adoptive brother, Jake, a dog with magical powers to change shape and size at will.

The season was storyboarded and written by Adam Muto, Sam Alden, Polly Guo, Seo Kim, Somvilay Xayaphone, Laura Knetzger, Steve Wolfhard, Tom Herpich, Graham Falk, Kent Osborne, Hanna K. Nyström, and Aleks Sennwald.

The series follows the adventures of Finn the Human (a boy) and his best friend, Jake, a dog with magical powers to change shape, grow, and shrink at will.

Common storylines revolve around Finn and Jake discovering strange creatures, dealing with the antagonistic-but-misunderstood Ice King, and battling monsters to help others.

"Ketchup"'s animation is by Alex and Lindsay Small-Butera, a husband-and-wife team known for their web series Baman Piderman.

[18] The season's main storyline writers included Jack Pendarvis, Adam Muto, Ashly Burch, Osborne, and Julia Pott.

[19] According to Pendarvis, after Burch left following the eighth season "Julia parachuted in at perhaps the most mind-boggling moment in the sweeping arc of the series just totally undaunted, and showed incredible spirit and ingeniousness that encouraged us to press forward.

"[20] Storyboard artists who worked on this season included Adam Muto, Sam Alden, Polly Guo, Seo Kim, Somvilay Xayaphone, Laura Knetzger, Steve Wolfhard, Tom Herpich, Graham Falk, Kent Osborne, Hanna K. Nyström, and Aleks Sennwald.

The season's voice actors included Jeremy Shada (Finn the Human), John DiMaggio (Jake the Dog), Tom Kenny (the Ice King), Hynden Walch (Princess Bubblegum), and Olivia Olson (Marceline the Vampire Queen).

Former storyboard artist Niki Yang voiced the sentient video-game console BMO in English and Jake's girlfriend, Lady Rainicorn, in Korean.

"[32] In addition to the regular cast members, episodes have guest voices by individuals from a range of professions, including actors, musicians, and artists.

Tom Scharpling reprised his role as Jake's brother, Jermaine, and Thu Tran returned as AMO in "Orb".

[44] The ninth season premiered on television on April 21, 2017, with "Orb", although the episode had been released on the Cartoon Network phone app a week earlier.

According to Sava, the miniseries helped return the viewers to the land of Ooo and re-center and reconfigure the characters' central relationships.

[57] Paste magazine's Zack Blumenfeld praised the miniseries, writing that Elements "is superior to and more cohesive than both Stakes and Islands, simultaneously a return to Adventure Time's surrealist roots and an emotional step forward".