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 Hayden Ezzy Fern Guest Voice Andy Milonakis N.E.P.T.R. Guest Voice Fred Melamed Gumbald Guest Voice Fred Seibert Executive Producer Kelly Crews Producer Tom Herpich Writer Steve Wolfhard Writer