The term 'Joker Portrayer' refers to two actors who have famously portrayed the Joker in films. The first is Jack Nicholson, who played the Joker in the 1989 film 'BATMAN'. He is known for his iconic performance and his memorable lines. The second is Cesar Romero, who played the Joker in the 1966 television series 'BATMAN'. He was the first actor to portray the Joker on screen and his performance set the standard for future portrayals.