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 Grey DeLisle Griffin voices Amanda / Monster Girl Chris Diamantopoulos voices Donald Ferguson Zachary Quinto voices Robot Khary Payton voices Black Samson Melise voices Kate Cha / Dupli-Kate Grey DeLisle Griffin voices Shrinking Rae Kevin Michael Richardson voices Mauler Twins Fred Tatasciore voices Adam Reginald VelJohnson voices Dean Winslow Fred Tatasciore voices Kill Cannon Mahershala Ali voices Titan Gary Anthony Williams voices GDA Scientist Michael Dorn voices Battle Beast Chris Diamantopoulos voices Isotope Jeffrey Donovan voices Machine Head Nicole Byer voices Vanessa Nicole Byer voices Fiona Fred Tatasciore voices The Mad Scientist