Who a character is on the inside is often not clear from their actions and interaction with the outside world at the beginning of a story. Often the inner-self has been suppressed so far inside of the character that they forget, fail to or are unable to recognise or express their true selves and it takes an extraordinary experience for them to initiate change.
Each of the key character types plays a specific role in a story, and there are five which you need to carefully craft into the fabric of your narrative, when designing your story. The protagonist, the antagonist, the mentor, the ally and the love interest.
Being an adaption of a book, and even more than that a classic, and even more than that a classic book that has been successfully adapted for the screen more than once; there is added pressure on the writer to both be faithful to the original material and to craft a good screenplay.
Parasite, written by director Bong Joon Ho with Han Jin Won, instantly sets up the social standing of the lead characters by setting the opening scene of the film in their “semi-basement home”. In Korea this is an immediate indication that they are poor, although there is some hope because they are not totally underground.
By the time JOKER reached the screen, director Todd Phillips had rearranged the opening scenes and they were no longer in the same sequence as they were in his original screenplay. He also interestingly added an opening scene that is not in the screenplay at all.