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 Grey DeLisle Griffin voices Amanda / Monster Girl Chris Diamantopoulos voices Donald Ferguson Khary Payton voices Black Samson Ross Marquand voices The Immortal Ross Marquand voices Rudolph "Rudy" Conners Seth Rogen voices Allen the Alien Jay Pharoah voices Zandale Randolph / Bulletproof Sterling K. Brown voices Angstrom Levy Mark Hamill voices Art Rosenbaum Clancy Brown voices General Kregg Ben Schwartz voices Shapesmith Calista Flockhart voices April Howsam Luke Macfarlane voices Rick Ben Schwartz voices Rus Livingston Scoot McNairy voices King Lizard Lincoln Bodin voices Oliver Grayson Kevin Michael Richardson voices Monster Kevin Michael Richardson voices Tech Trooper #1 Khary Payton voices Martian Leader Ross Marquand voices Proprietor Ben Schwartz voices Tech Trooper #2 Grey DeLisle Griffin voices Helga Grey DeLisle Griffin voices Nurse Chris Diamantopoulos voices GDA Med Tech Co Starring Ami Shukla voices Additional Voices Nyima Funk voices Additional Voices Robert Kesselman voices Additional Voices Dan Navarro voices Additional Voices