Title: The Dark Knight (film)
Content:  Joker: ; A psychopathic illegalist mastermind portraying himself as an "agent of chaos", who rises from the criminal underworld by thrusting Gotham into anarchy and drawing Batman ever closer to crossing the fine line between heroism and vigilantism. Before Ledger was cast in July 2006, Paul Bettany, Lachy Hulme, Adrien Brody, Steve Carell, and Robin Williams publicly expressed interest in it. However, Nolan had wanted to work with Ledger on a number of projects in the past (including unsuccessfully approaching Ledger for the role of Batman in Batman Begins) and was agreeable to Ledger's chaotic interpretation of the character. 
Title: Joker (The Dark Knight)
Content:  The Joker is a fictional character who appears in Christopher Nolan's 2008 superhero film The Dark Knight, based upon the DC Comics character and supervillain of the same name. He was portrayed by Heath Ledger. A psychopathic criminal mastermind and mass murderer with a warped, sadistic sense of humor, the Joker is hired by Gotham City's mob bosses to kill the vigilante Batman (Christian Bale), and also comes into conflict with Batman's allies, Gotham police officer James Gordon (Gary Oldman) and district attorney Harvey Dent (Aaron Eckhart). The Joker embodies themes of chaos, anarchy and obsession: throughout the film, he expresses a desire to upset 
Title: The Dark Knight (film)
Content:  cast includes Nydia Rodriguez Terracina as Judge Janet Surrillo, and Tom "Tiny" Lister Jr. as a prison inmate on one of the bomb-rigged ferries. Vincenzo Nicoli played a crime boss in the meeting that had been held by the Joker and Lau. William Fichtner played the Gotham National Bank manager, and Cillian Murphy returns in a cameo as Jonathan Crane / Scarecrow, who is apprehended early on in the film by Batman. Musician Dwight Yoakam was approached for the roles of either the manager or a corrupt cop, but he chose instead to focus on his album Dwight Sings 
Title: Joker (The Dark Knight)
Content:  The character is indirectly referenced at the end of Batman Begins, when Lt. James Gordon (Gary Oldman) describes to Batman (Christian Bale) a suspect wanted in connection with an armed robbery and double homicide. Gordon shows Batman a joker playing card left at the crime scene. The Joker first appears in person at the beginning of The Dark Knight, as part of a six-member gang wearing clown masks who rob a mob-owned bank. He tricks four of them into killing each other, then kills the last one himself and escapes with the money. Interrupting a videoconference between mob bosses Sal Maroni (Eric Roberts), the Chechen (Ritchie Coster) and Gambol (Michael Jai White) with their accountant 
Title: Batman (TV series)
Content:  The opening scene of The Dark Knight, the second installment of Christopher Nolan's Batman film series, The Dark Knight Trilogy, showcases a bank robbery by the Joker. Throughout the sequence, he wears a clown mask which is reminiscent of the one worn by Cesar Romero in "The Joker Is Wild!", his very first appearance as the Joker in the series.
Title: Joker (Jack Napier)
Content:  Heath Ledger, who portrayed the character in Christopher Nolan's 2008 film The Dark Knight, has cited Nicholson's portrayal as an influence on his interpretation of the character, stating "This character was too good to turn down. And yes, it would be a crime to attempt to [step in or to] follow Jack Nicholson's footpath that he so heavily stands into my memory of The Joker. I mean, I adore what he did and him in general." Mark Hamill, who voiced the character in Batman: The Animated Series, as well as in the Batman: Arkham video game series, has also cited Nicholson's adaptation of the character as an influence, but was told by show producers to avoid using Nicholson's Joker as a direct source of inspiration.
Title: Joker (The Dark Knight)
Content:  On 31 July 2006, The Dark Knight was officially announced by Warner Bros with the casting of Heath Ledger as the Joker. The casting decision surprised some and was seen as a controversial move at the time, receiving notable negative reactions on the Internet. Nolan remembered the cynicism he endured surrounding Ledger's casting, saying that "the whole world turned around and said 'What are you doing?' You know, Heath Ledger, Joker, didn't make any sense to people at all." In his 2016 book The Caped Crusade: Batman and the Rise of Nerd Culture, NPR contributor Glen Weldon recalled that fans were outraged over the choice 
Title: Joker (character)
Content:  by John DiMaggio in 2010's Batman: Under the Red Hood and 2020's Batman: Death in the Family, and by Michael Emerson in 2012's two-parter The Dark Knight Returns. The television series Gotham (2014–2019) explores the mythology of the Joker through twin brothers Jerome and Jeremiah Valeska, played by Cameron Monaghan. Jared Leto portrays the Joker in the DC Extended Universe, beginning with Suicide Squad (2016); Leto reprised the role in Zack Snyder's Justice League (2021). Zach Galifianakis voiced the character in The Lego Batman Movie (2017). The 2019 film Joker focuses on the origins of the Joker as portrayed by Joaquin Phoenix. Although the film was controversial 
Title: Batman in film
Content:  Christopher Nolan reprised his duties as director, and brought his brother, Jonathan, to co-write the script for the second installment. The Dark Knight featured Christian Bale reprising his role as Batman/Bruce Wayne, Heath Ledger as The Joker, and Aaron Eckhart as Harvey Dent / Two-Face. Principal photography began in April 2007 in Chicago and concluded in November. Other locations included Pinewood Studios, Ministry of Sound in London and Hong Kong. On January 22, 2008, after he had completed filming The Dark Knight, Ledger died from an accidental overdose of prescription medication. Warner Bros. had created a viral marketing campaign for The Dark Knight, developing promotional websites and trailers highlighting screen shots of Ledger as the Joker, but after Ledger's death, the studio refocused its promotional campaign. The film depicts Batman fighting The Joker, aided by the prosecution of charismatic District Attorney Harvey Dent. 
Title: Batman
Content:  character. In 2016, Ben Affleck began portraying Batman in the DC Extended Universe with the release of the film Batman v Superman: Dawn of Justice, directed by Zack Snyder, a younger child version of the character was played by Brandon Spink in the same film. Affleck also made a cameo appearance as Batman in David Ayer's film Suicide Squad (2016). Affleck reprised the role in the 2017 film Justice League, also set in the DC Extended Universe. Dante Pereira-Olson portrays a young Bruce Wayne in the 2019 film Joker. In 2019, Robert Pattinson was cast to play Batman in the upcoming, The Batman, releasing in 2022.

Question: who plays joker in batman the dark knight?
Answer: Ledger.