Believed to be born in Gotham City, Arthur was abandoned as a baby in his very early days of life and had been adopted by a young woman named Penny Fleck, who poorly raised her son. She allowed him to be beaten by her boyfriend and the young boy was tied to a heater and left to starve for days on end. Arthur suffered severe head trauma that was believed to have given him his laughing disorder, which he was told was a condition by his mother for most of his life. He was a very lonely individual where his only company was his mother and a pet cat, longing for a romantic relationship that he had never gotten. While he was still aware of being abused in his adolescent years, the memories remained clouded for decades.
Suffering memory loss of his childhood, Arthur spent the majority of his life living with his mother and taking care of her in her old age while he worked jobs to keep their rundown apartment. Longing for a loving father figure in his life, Arthur had seen the likes of night television show host Murray Franklin and billionaire Thomas Wayne as two of his father figures, even daydreaming of being on the Murray Franklin Show and being called out of the audience to walk up on stage, where Murray said he wished he had a son just like Arthur.
Working as a stand-up comedian, his job suffered when he was jumped by street punks and the property manager’s sign was destroyed. His trail to crime would begin after his co-worker Randall had given him a .38 revolver after the mugging incident. Growing more lonely, Arthur romantically fantasized about his neighbor Sophie, even following her to her daughter's school one evening and on the subway train back. Inviting her to his stand-up comedy show, Sophie did not seem too thrilled, but he imagines her being there, and the only one laughing at his jokes before he began uncontrollably laughing in hysterics once again in front of a crowd of people and is then kicked off of the stage. Arthur's attempts to resurrect his career had failed time and time again, the last when he dropped his .38 in the middle of doing his clown act for children at a cancer hospital where he was fired from Ha-Ha’s for good, where Arthur snitched on Randall for giving him the .38 in the first place.
After losing his therapist and his access to his psychiatric medications, Arthur lost his sanity and shot and killed three Wallstreet boys on a subway train for laughing at a woman and beating on Arthur for his misunderstood laughing disorder. The so-called murderous clown on the subway train gained local fame, and also infamy within the wealthy, and soon sparked a riot in Gotham city of ‘Kill the rich’ where some of the working class began to wear their own clown masks and saluted the anonymous subway killer clown and looked down on the snobby Thomas Wayne who degraded the poor on public television and it was then, Arthur lost respect for him.
He later on believed Thomas Wayne was his father after reading a letter he found written by his mother claiming that Arthur is his son and an old photo of his mother with a note written on the back signed by Thomas himself, reading "love your smile". Arthur gets into a heated argument with Penny about her lying to him all of these years, and his mother held her beliefs that Thomas was a good man and that he could help them financially.
Arthur visited Wayne Manor the next day, where he met Thomas’s young emotionless son, Bruce. Forcing a smile on his face when he saw how expressionless the child was, a then young Alfred intervened. Arthur asked about Thomas Wayne being his father and stated that his mother Penny once worked for Wayne, but Alfred denied it and claimed he knew Penny and that she had lied about having an affair with Wayne. Nearly choking out Alfred in anger through the manor's closed gates, Arthur fled from the scene.
Two detectives Burke and Garrity came in to question Arthur about the subway murders at his apartment who had just lost his job earlier that day making him a possible suspect. Getting them both to leave, Penny fell ill while Arthur was away and is hospitalized. Seeing Murray airing Arthur’s stand-up comedy broadcast, it turned out to be just to mock him, which deeply displeased the failed comedian, adding fire to his inner rage.
Arthur confronted Wayne after a charity theatre show in the bathroom, exclaiming to Wayne that Arthur is his son. When Thomas denies it, he claims Arthur was adopted and he never slept with Arthur’s mother and she was also -committed to Arkham State Hospital. Arthur had grown defensive of his mother and questioned why Wayne was lying. asking why people were so rude, also pleading for him to be a father to him. Arthur began laughing in hysterics directly in Thomas’s face only to be sucker-punched by the billionaire, threatening to kill Arthur if he ever touched his son Bruce again.
Growing into a deeper depression, Arthur stripped to his underwear and enclosed himself into his refrigerator after emptying its contents. After spending time masturbating in bed, he is phoned by a representative from the Murray Franklin Show to appear as a guest which Arthur accepts. But he knew there were more mysteries to be found. After discovering his mother’s records at Arkham State Hospital in a folder he had stolen from the clerk at the hospital archives, he uncovered the hard truth that he had been abandoned as a child, adopted and abused by his mother’s boyfriend when he was a boy and that the head trauma from his injuries may have caused his laughing condition. Arthur grew enraged by the reveal, feeling as if he had been lied to his whole life by the only person he truly loved. Returning to his mother at the hospital, Arthur smothered Penny in her own bed after speaking about how long he thought his life was a tragedy, and now he believes it is ‘a fucking comedy’.
Arthur goes back home and breaks into Sophie's apartment. She sees him and is terrified, asking him to leave for the sake of her daughter. Through this, it is revealed that every other moment featuring Sophie was just in Arthur's head as he was imagining happier possibilities.
Returning home, Arthur was visited by his co-workers Randall and Gary as they attempted to cheer him up prior to his mother’s death. Arthur pulled a trick once he was told detectives Garrity and Burke were returning, stabbing the much taller Randall with a pair of scissors, then bashing his head against the wall near his apartment door until he stopped struggling. Sparing Gary’s life, since Gary was the one who was nice to Arthur, who also found it to be an unfair fight in general. Giving him a kiss on the forehead and allowing him to leave unharmed, Arthur had unlocked the door for him since he was too short to reach. Donning a burgundy suit and applying his makeup to get ready for his appearance on Murray Franklin, the two detectives catch Arthur dancing on the street and pursue the man to arrest him. Slipping into the subway, the clown protesters beat up the detectives, allowing Arthur to escape.
Appearing on the Murray Franklin show as ‘Joker’ as he requested, Arthur exits the curtains as he had been rehearsing before. Confessing about the subway murders or so the audience thought, everyone was oblivious to his seriousness for a brief moment. Arguing that the audience only cares about the victims because Thomas Wayne spoke for them and anyone like Arthur was being ignored and walked over, the crowd scolded Arthur before he shot Murray point-blank in the head causing the wall behind him to be painted in blood. As the seats emptied, the news of Franklin's murder was quick to spread. Grabbing the camera lens, Arthur says, "Goodnight! And always remember, that's life!"
Thomas and Martha Wayne are murdered in front of Bruce by a clown protester shortly after they had left the movie theater, thus birthing Batman. Upon being driven to jail, two clown protesters in an ambulance had rammed into the police car to help free Arthur from being incarcerated. Respectfully resting Arthur on the hood of the police car once they discovered the two policemen were dead, the newly found Joker had risen, smearing the blood that oozed out of his nose across the corners of his mouth, where The Joker was finally born and those very protesters would possibly become The Joker’s henchmen, giving him the recognition he craved for. Arthur Fleck was no more.
- Imaginative - Imagines scenarios when he zones out, usually of happier possibilities
- Smokes often
- Uncontrollable laughter
- Passion for dancing
- looking for an emotional connection
- Later on, he develops a trait to kill people who wrong him. From the three Wall street boys on the subway, Randall, his former co-worker who set him up twice in the film, and lastly television show host Murray Franklin, Arthur's former father figure who he kills on camera after being invited on Franklin's nighttime talk show.
Arthur Fleck began as a lonely individual who had dreams of becoming a stand-up comedian. He longed for a romantic relationship throughout his life, that he seemed to never have gotten. He had a compassionate mother and son relationship with his mother Penny Fleck until he found out the latter lied to him and abused him as a child.Fleck in the beginning appeared to be a kind but troubled man with a forgotten dark past who for the longest time went by his mother’s words that he was brought to bring joy and laughter. Arthur is depicted as a chain smoker with a poor diet.
After Arthur is pushed to the brink and had no one else important in his life once he killed his mother out of rage, he was willing to murder anyone who wronged him in any way as his empathy had dissipated with his good nature once he became the Joker after he assassinated Murray Franklin on live television.
- Penny Fleck - Mother and victim; deceased.
- Sophie - Neighbor.
- Murray Franklin - Idol and victim; deceased.
- Thomas Wayne - Alleged father turned enemy; deceased.
- Bruce Wayne - Alleged brother turned enemy.
- Gary - Former co-worker.
- Randall - Former co-worker and victim; deceased.
Behind the scenes
- Joaquin Phoenix lost 52 pounds for the role.
- Phoenix had came up with his own signature Joker laugh for the film after months of practice.
- In true Joker fashion, it is shown throughout the movie that Arthur is an unreliable narrator, as it is revealed his relationship with his neighbor was completely imagined.