 " Walnuts & Rain " was written and Storyboarded by Tom Herpich , from an outline by head Adventure Time writer Kent Osborne , series creator Pendleton Ward , Jack Pendarvis , showrunner Adam Muto , and Herpich . Andres Salaff served as the episode 's supervising director , while the art direction was helmed by Nick Jennings . The episode marks Herpich 's first solo storyboard since season three 's ' Thank You " . Near the latter part of season six , Herpich and has storyboard partner Steve Wolfhard each had episode ideas that they wanted to work on . The two decided to temporarily dissolve their partnership and work on episodes individually ( Wolfhard would go on to create " Graybles 1000 + " ) . Herpich had been working on the outline for " Walnuts & Rain " on and off for several months before he finally storyboarded it , and he would later describe the episode as an " allegorical escape story " , similar to the season five episodes " Puhoy " and " Dungeon Train " . This episode guest stars musician Chris Isaak as Seven , and Matt L. Jones as King Huge . Jones had previously appeared in the first season episode " Memories of Boom Boom Mountain " voicing the crying Mountain . 
