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 Chris Diamantopoulos voices Donald Ferguson Zachary Quinto voices Robot Melise voices Kate Cha / Dupli-Kate Seth Rogen voices Allen the Alien Clancy Brown voices Damien Darkblood Jon Hamm voices Steve Max Burkholder voices Matt Kevin Michael Richardson voices Dr. Barclay