In the Mega Man original series, a Robot Master is a special kind of robot that possesses a very advanced level of artificial intelligence. The Robot Master AI system is credited to Dr. Light. Most Robot Masters possess a unique identification code, consisting of a two-letter "series code" followed by one of N, No, or #, then a three-digit "serial number". Most, if not all, Robot Masters possess a Special Weapon. These powers can be gained after the robot is defeated. Robot Masters can also be grouped into types depending on what elemental nature their power and environment may be. Some Robot Masters (usually in Mega Man 8 or Mega Man & Bass) have an overdrive system, which gives them the ability to perform a new attack when their health has been knocked down to a certain level. With the exception of Roll, Splash Woman and Quake Woman, (and Centaur Man in the manga) all Robot Masters are male.