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 Andy Ristaino, Cole Sanchez, Tom Herpich, Steve Wolfhard, Seo Kim, Somvilay Xayaphone, Graham Falk, Derek Ballard, Jesse Moynihan, Masaaki Yuasa, Adam Muto, Kent Osborne, Lyle Partridge, Bert Youn, Madeleine Flores, Jillian Tamaki, Sam Alden, Sloane Leong, Brandon Graham, and David Ferguson.

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

[1] This season's main story arc, however, deals with Finn discovering the true identity of his human father, and his subsequent attempts to reconnect with him.

[2] The season ends with Princess Bubblegum being deposed by the King of Ooo (voiced by Andy Daly), and Finn fighting the primordial cosmic space demon Orgalorg (the actual identity of Gunter the penguin).

[12] The season was storyboarded and written by Andy Ristaino, Cole Sanchez, Tom Herpich, Steve Wolfhard, Seo Kim, Somvilay Xayaphone, Graham Falk, Derek Ballard, Moynihan, Yuasa, Adam Muto, Kent Osborne, Lyle Partridge, Bert Youn, Madeleine Flores, Jillian Tamaki, Sam Alden, Sloane Leong, Brandon Graham, and David Ferguson.

[14] He once again left the series after the conclusion of its fourth season to focus his attention on Studio Spiyo in Seoul, South Korea.

[25] The voice actors for the season include: 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 voices the sentient video game console BMO in English, as well as Jake's girlfriend Lady Rainicorn in Korean.

The Lich is portrayed by Ron Perlman in his demonic form,[29] and by Ethan Maher as a large baby after the events of the season premiere.

"[34] In addition to the regular cast members, episodes feature guest voices from many ranges of professions, including actors, musicians, and artists.

The season openers, "Wake Up" and "Escape from the Citadel", feature the return of Kumail Nanjiani as Prismo, M. Emmet Walsh as the Cosmic Owl, and Miguel Ferrer as Death and one of the heads of Grob Gob Glob Grod.

[43] Comedian Melinda Hill reprises her role as Doctor Princess in the episode "Breezy",[44] which also features the vocal talents of Ashly Burch as the titular character.

[50][51] "Something Big" also sees the return of Keith Ferguson as Colonel Candy Corn; he would also reprise this role in several other season six episodes.

[46] Kristen Schaal and Dan Mintz reprise their roles as Jake Jr. and T.V., respectively, in "Ocarina", and the episode also sees the introduction of Marc Evan Jackson and Paget Brewster as Kim Kil Whan and Viola, respectively.

[52][53] Duncan Trussell, Steve Little, Dana Snyder, and series storyboard artist Cole Sanchez, return in "Thanks for the Crabapples, Giuseppe!

[58][59] In "Dentist", Collin Dean reprises his role as Tiffany, Lucy Lawless guest stars as the Queen of the Ants, and Andy Daly plays Lieutenant Gamergate.

[60][61][62] Daly also reprises his role as the King of Ooo in "Gold Stars" and the first part of the season finale, "Hot Diggity Doom".

[64] "Evergreen" guest stars Pamela Adlon, Alan Tudyk, and Keith David as Gunter, Chatsberry, and Balthus, respectively.

[65] "Gold Stars" sees the introduction of Paul Scheer as Toronto, a character who would also appear in "Hot Diggity Doom".

[25][72] "Chips & Ice Cream" guest stars Ron Livingston, Riki Lindhome, and Kate Micucci; the latter two comprise the comedy band Garfunkel and Oates.

[80] Various minor and background characters are voiced by Tom Kenny, Dee Bradley Baker, Maria Bamford, Steve Little, and Kent Osborne.

Eric Kohn of IndieWire applauded the two-part season opener, "Wake Up" and "Escape from the Citadel", for taking a darker turn in regards to the series' storytelling.

Coupled with deep dives into the history of Ooo and the increasing visual confidence of episodes like the surreal, breathtaking 'Food Chain,' Adventure Time appears ready to use its considerable heft and years of laying narrative foundations to do some of TV's finest storytelling about grappling with the past and accepting the responsibilities of adulthood.

[98] Masaaki Yuasa and Eunyoung Choi were both nominated for an "Outstanding Achievement, Directing in an Animated TV/Broadcast Production" Annie Award for their work on "Food Chain".

[99] "Food Chain" was later selected for competition at the 2015 Annecy International Animated Film Festival,[100][101] On April 23, 2015, it was announced that the series had won a Peabody Award for Best Children's Programming.

[143][144][145] Several other DVD compilations, including Finn the Human, Frost & Fire, The Enchiridion, and Card Wars were also released that contained episodes from the sixth season.