Pendleton Ward Lumpy Space Princess Creator, Voice Jeremy Shada Finn Voice John DiMaggio Jake Voice Hynden Walch Princess Bubblegum Voice Tom Kenny The Ice King Voice Olivia Olson Marceline Voice Niki Yang BMO Guest Voice Polly Lou Livingston Tree Trunks Guest Star Andy Milonakis N.E.P.T.R. Guest Voice Jenny Slate Huntress Wizard Guest Voice Marc Evan Jackson Kim Kil Whan Guest Voice Hayden Ezzy Fern Guest Voice Felicia Day Betty Grof, Past Betty Guest Voice Jessica DiCicco Flame Princess Guest Voice Fred Melamed Gumbald Guest Voice Brad Neely The Green Knight Guest Voice Ron Lynch Mr. Pig Guest Star Maria Bamford Aunt Lolly, Manfried Guest Voice Dave Foley Shapeshifter Guest Voice Cole Sanchez Teen Randy Guest Voice Fred Seibert Executive Producer Kelly Crews Producer Graham Falk Writer Sam Alden Writer Hanna Nystrom Writer Seo Jung Kim Writer Tom Herpich Writer Aleks Sennwald Writer Steve Wolfhard Writer Somvilay Xayaphone Writer Patrick McHale Writer Kent Osborne Writer Erik Fountain Writer Adam Muto Writer Polly Guo Writer