In the movie ‘Joker’, there is an expression of Joaquin Phoenix that tells it all. It essentially captures the complete loss of his innocence, and his belief in the world. He is alone in his thoughts in a made up world and all his psychotic mind can think of is the destruction of the world outside. Something similar happens to Pvt.Pyle (Vincent D’Onofrio), when he loses his faith in everybody and just snaps.
These two expressions of two very good actors are quite different, understandably as one is about to self-destruct and is sure about it (Pvt.Pyle), while the other (Arthur Fleck aka Joke) looks it at like the start of a dangerous game. This perspective of ‘Full Metal Jacket’ and Pvt.Pyle comes very handy in understanding the portrayal of Joker by Joaquin Phoenix, who internalizes everything except the laughter as if it were a defense mechanism or an appearance and his every hurt comes to haunt him in mega proportions which he unleashes on the real world.
In the end what we have is a mad man, who looks at his moves as funny and questions who are others to decide what is funny. But there is question about the performance of Oscar winner Joaquin Phoenix, which is serious and spectacular in each and every frame.