"Put on a happy face."
Joker - Easter Eggs & Hidden Details
Easter Eggs
During a scene where Arthur is at a lavish event, a clip from a Charlie Chaplin film, "Modern Times" (1936), is shown playing to the wealthy audience.
This is a significant thematic reference. "Modern Times" is a comedy about Chaplin's 'Little Tramp' character struggling to survive in a modern, industrialized society that is indifferent to his plight. By showing the rich laughing at the struggles of the 'Little Tramp', the film draws a direct parallel to how society, and particularly the elite, views Arthur's own suffering as a joke, reinforcing the theme of class insensitivity.
The clown masks worn by the protestors throughout Gotham become a symbol of a populist uprising against the rich.
This mass adoption of a mask as a symbol for a political movement has been compared to the real-world use of the Guy Fawkes mask (popularized by the film "V for Vendetta") by the activist group Anonymous and other protest movements worldwide. It reflects how a fictional symbol can be embraced by a real-world disenfranchised group to represent their rebellion.