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 Khary Payton voices Black Samson Zachary Quinto voices Robot Melise voices Kate Cha / Dupli-Kate Grey DeLisle Griffin voices Shrinking Rae Kevin Michael Richardson voices Mauler Twins Clancy Brown voices Damien Darkblood Chris Diamantopoulos voices Doc Seismic