Guest Stars Walton Goggins voices Cecil Stedman Zazie Beetz voices Amber Bennett Gillian Jacobs voices Samantha Eve Wilkins / Atom Eve Andrew Rannells voices William Clockwell Jason Mantzoukas voices Rex Sloan / Rex Splode Chris Diamantopoulos voices Donald Ferguson Grey DeLisle Griffin voices Amanda / Monster Girl Zachary Quinto voices Robot Khary Payton voices Black Samson Ross Marquand voices The Immortal Melise voices Kate Cha / Dupli-Kate 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 Ross Marquand voices Omnipotus Rhea Seehorn voices Andressa Rob Delaney voices Nuolzot/Séance Dog Kevin Michael Richardson voices Monster Peter Cullen voices Thaedus Chris Diamantopoulos voices Jerry Melise voices Iguana Kari Wahlgren voices Announcer Kari Wahlgren voices GDA Agent Kari Wahlgren voices Female Thraxan Jay Pharoah voices Komodo Dragon Jay Pharoah voices Sergeant Kevin Michael Richardson voices Male Thraxan Khary Payton voices Martian Ben Schwartz voices Corey 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