Guest Stars Hynden Walch voices Bonnie Olivia Olson voices Marceline Audrey Bennett voices Young Marceline Stephen Root voices Martin Mertens Billy Brown voices Vampire King Jenny Slate voices Huntress Erica Luttrell voices Hana Abadeer Jeremy Shada voices Baby Finn Co Starring Dee Bradley Baker voices Additional Voices Cree Summer voices Additional Voices Jinkx Monsoon voices Additional Voices Steve Little voices Additional Voices Cole Sanchez voices Additional Voices