"The Joker" spoilers reveal Joaquin Phoenix's full costume and makeup as the Clown Prince of Crime. New behind-the-scenes footage of the film was posted online, featuring Phoenix as Joker causing havoc in one of Gotham City's subway stations.

Twitter user Amanda posted a photo of Thomas Wayne running for Gotham's mayor in the film. "The Joker" spin-off centers around Batman's most notorious enemy, who was once a failed stand-up comedian as the pressures of life drove him to become a criminal.

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It severely affected his psyche along the way. The film is also separate from the DC Extended Universe, being a stand-alone origin story. A "Suicide 2" script draft is also complete as well [VIDEO].

Phoenix is the fifth actor to portray Joker in the live-action films, joining Cesar Romero, Jack Nicholson, Heath Ledger, and Jared Leto.

Joker on Gotham's subway

According to Comic Book, the online video (shown below) depicts Phoenix as The Joker, making a little chaos at a subway station. Several people wearing clown masks start attacking civilians, as Joker casually exits the train and takes off his mask, showing his full makeup and classic purple suit.

Phoenix told Collider, in a previous interview, that he wanted his version of the Clown Prince of Crime to be unique and to stand out from the previous versions in every media [VIDEO]. His version is named Arthur Fleck, and the story will have elements of the classic Batman comic book arc, "The Killing Joke," which tells how Arthur became a criminal and how his first encounter with the Dark Knight changed him forever.

"I think, underneath the excitement of these films, and the size of them, there are these incredible characters that are dealing with real life struggles," Phoenix said. "And sometimes that is uncovered and exposed, and sometimes it isn’t, and so I always felt, like, there were characters in comics that were really interesting and deserve the opportunity to be kind of studied."

Thomas Wayne runs for Mayor

According to Screen Rant, Amanda tweeted a poster of Thomas Wayne's campaign with the slogan "Moving Gotham Forward."

In the comics, Thomas is a medical doctor and co-founder of Wayne Enterprises. The Wayne family is one of the richest and most influential families in Gotham, and has dedicated their lives to make the city safe and innovative despite the increasing crime rates.

"Narcos" star Brett Cullen has been cast for the role of Thomas, and has close ties with Arthur in the movie. "The Joker" spin-off will premiere in cinemas on October 4, 2019.