The term "Mad King" often refers to historical rulers who exhibited erratic behavior or mental instability. One of the most famous examples is King George III of Britain, who faced episodes of madness during his reign in the 18th century. His condition affected his ability to govern, leading to significant political challenges, including the loss of the American colonies. In popular culture, the phrase has been used to describe characters in literature and media, such as King Aerys II Targaryen from George R.R. Martin's series, A Song of Ice and Fire. These portrayals often emphasize themes of power, madness, and the consequences of unstable leadership.