<P> Storyboard artists who worked on this season include: Tom Herpich, Steve Wolfhard, Jesse Moynihan, Laura Knetzger, Kris Mukai, Emily Partridge, Graham Falk, Charmaine Verhagen, Sam Alden, Pendleton Ward, Seo Kim, Somvilay Xayaphone, Hanna K. Nyström, Ako Castuera, Aleks Sennwald, Polly Guo, Kent Osborne, and Adam Muto . This was the final season to feature several long - serving storyboard artists and production crew members . Moynihan left the show after completing "Normal Man" to finish his web comic Forming . Finally, supervising director Andres Salaff left after this season to storyboard on Cartoon Network's series Uncle Grandpa . Conversely, the season also saw the return of former storyboard artist Ako Castuera (who returned to storyboard the episode "Broke His Crown" with Nyström before working as a storyboard revisionist, starting with "Two Swords"). and former storyboard artist and creative director Cole Sanchez (who took the position of one of the series' supervising directors starting with "Two Swords"). </P> <P> During the eighth season of Adventure Time, the miniseries Islands aired at the end of January and the beginning of February 2017 . This event was first hinted at before the airing of the first Adventure Time miniseries Stakes (2015) when head story writer Kent Osborne revealed that the show would likely produce several more miniseries . Islands tells the story of Finn, Jake, BMO (voiced by Niki Yang) and Susan Strong (voiced by Jackie Buscarino) leaving Ooo and traveling across the ocean to solve the mystery of Finn's past . During their trip, they encounter various creatures, new friends, and a variety of mysterious islands . The voyage culminates with a trip to Founder's Island, where Finn learns what happened to the rest of the human race and meets his mother, Minerva (voiced by Sharon Horgan). </P> <P> The season's voice actors 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). Ward himself provides the voice for several minor characters, including Lumpy Space Princess . Former storyboard artist Niki Yang voices the sentient video game console BMO in English, as well as Jake's girlfriend Lady Rainicorn in Korean . Polly Lou Livingston, a friend of Pendleton Ward's mother, Bettie Ward, plays the voice of the small elephant Tree Trunks . Jessica DiCicco voices Flame Princess, Finn's ex-girlfriend and the sovereign of the Fire Kingdom . Andy Milonakis voices N.E.P.T.R., a sentient robot who makes and throws pies . Justin Roiland provides the voice of the Earl of Lemongrab . Several episodes, including most of the episodes in the Islands miniseries, feature Jackie Buscarino, who voices Susan Strong . The Adventure Time cast records their lines together as opposed to doing it individually . This is to capture more natural sounding dialogue among the characters . Hynden Walch has described these group session as akin to "doing a play reading--a really, really out there play ." </P> <P> In addition to the regular cast members, episodes feature guest voices from a range of professions, including actors, musicians, and artists . In the season opener "Broke His Crown", both Lena Dunham and Pamela Adlon reprise their characters Betty and Gunter the dinosaur . Dan Mintz, Henry Rollins, and Laura Silverman return to reprise their roles as T.V., Bob, and Ethel in "Lady Rainicorn of the Crystal Dimension". This episode also features former storyboard artist Bert Youn and comedian Fred Stoller voicing the rainicorns Lee and Roy . The episode "I Am a Sword" guest stars Amy Sedaris, Agee, and Melinda Hill; Sedaris plays Bandit Princess, Agee plays a Merchant and Science Cat, and Hill plays Space Bear and Sharon the spiky person . Storyline writer Ashly Burch plays Bun Bun in the titular episode, which also features Keith David reprising his role as the former Flame King . In "Elemental", Lauren Lapkus is introduced as the voice of ice elemental, Patience St. Pim . "Five Short Tables" sees the return of Madeleine Martin, Roz Ryan, Donald Glover, Grey DeLisle, and Emo Philips; they voice Fionna, Cake, Marshall Lee, Ice Queen, and Cuber . The episode also guest stars Hannibal Buress as Flame Prince, Crispin Freeman as Turtle Prince and Ice President, Keith Ferguson as Prince Gumball (standing in lieu of the character's original voice actor, Neil Patrick Harris, who was unavailable due to prior commitments), and Elle Newlands as Butterscotch Butler . "The Music Hole" features several guest actors, including Ashley Eriksson as the titular Music Hole, and Jackie Buscarino as Susan Strong . Alia Shawkat voices Charlie, Rich Sommer voices Grand Prix, and Reggie Watts voices the turtle announcer in "Daddy - Doughter Card Wars". "Preboot" sees the return of Buscarino as Susan Strong and Collin Dean as Tiffany; the episode also introduces Lennon Parham as Dr. Gross . Rainn Wilson reprises his role as Rattleballs, as well as voicing the adult version of Sparkle in "Reboot". The episode "Two Swords" introduces the character of Fern, voiced by Hayden Ezzy . The next episode, "Do No Harm", sees both Jeff Bennett and Hill reprise their roles as the Grass Wizard and Doctor Princess, respectively . In "Wheels", Marc Evan Jackson reprises his role as Kim Kil Whan, and Rae Gray guest stars as Jake's granddaughter, Bronwyn . Ron Lynch returns as Mr. Pig in "High Strangeness". "Horse & Ball" features British animator James Baxter, who voices the horse of the same name . Alan Tudyk returns to voice the character Chatsberry in "Jelly Beans Have Power". The Islands miniseries features Josh Fadem as Whipple the sea - dragon, Helena Mattsson as Alva, Reggie Watts as Vinny, Jasika Nicole as Frieda, Livvy Stubenrauch as young Kara / Susan, Sharon Horgan as Finn's mother Minerva, and Laraine Newman as the Widow . The miniseries also sees Lennon Parham reprise her role as Dr. Gross and Stephen Root return to voice Finn's father, Martin . </P>

Adventure time season 8 episode 20 full episode