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 Khary Payton voices Black Samson Zachary Quinto voices Robot 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 Kevin Michael Richardson voices Mauler Twins Mark Hamill voices Art Rosenbaum Gary Anthony Williams voices GDA Scientist