Guest Stars Walton Goggins voices Cecil Stedman Zazie Beetz voices Amber Bennett Gillian Jacobs voices Samantha Eve Wilkins / Atom Eve Jason Mantzoukas voices Rex Sloan / Rex Splode Andrew Rannells voices William Clockwell Grey DeLisle Griffin voices Amanda / Monster Girl Chris Diamantopoulos voices Donald Ferguson Zachary Quinto voices Robot Khary Payton voices Black Samson Melise voices Kate Cha / Dupli-Kate Ross Marquand voices The Immortal Ross Marquand voices Rudolph "Rudy" Conners Grey DeLisle Griffin voices Shrinking Rae Seth Rogen voices Allen the Alien Jay Pharoah voices Zandale Randolph / Bulletproof Ben Schwartz voices Shapesmith Cliff Curtis voices Paul Ben Schwartz voices Rus Livingston Scoot McNairy voices King Lizard Kevin Michael Richardson voices Monster Rhea Seehorn voices Andressa Rob Delaney voices Nuolzot/Séance Dog Ross Marquand voices Omnipotus Peter Cullen voices Thaedus Kari Wahlgren voices Female Thraxan Kari Wahlgren voices GDA Agent Kari Wahlgren voices Announcer Kevin Michael Richardson voices Male Thraxan Melise voices Iguana Khary Payton voices Martian Jay Pharoah voices Sergeant Jay Pharoah voices Komodo Dragon Ben Schwartz voices Corey Chris Diamantopoulos voices Jerry Nyima Funk voices Bridget Co Starring Nyima Funk voices Additional Voices Ami Shukla voices Additional Voices Robert Kesselman voices Additional Voices Dan Navarro voices Additional Voices