Social Worker: What's so funny?
Arthur Fleck: I was just thinking... just thinking of a joke.
Social Worker: Do you wanna tell it to me?
Arthur Fleck: You wouldn't get it.
Social Worker: They don't give a shit about people like you, Arthur. And they don't give a shit about people like me either.
Arthur Fleck: My mother always tells me to smile and put on a happy face. She told me I had a purpose: to bring laughter and joy to the world.
Police Officer: The whole city's on fire 'cause of you.
Arthur Fleck: I know. Isn't it beautiful?
Arthur Fleck: Please, I don't support that language, just don't... DON'T.
Arthur Fleck: Ugh, why is everybody so upset about these guys? If it was me dying on the sidewalk, you'd walk right over me! I pass you every day and you don't notice me. But these guys. What? Because Thomas Wayne went and cried about them on TV? Playing my video. Inviting me on the show. You just wanted to make fun of me. You're just like the rest of 'em.
Murray Franklin: I'm waiting for the punchline.
Arthur Fleck: There is no punchline.
Arthur Fleck: I killed those guys because they were awful. Everybody is awful these days. It's enough to make anyone crazy.
Arthur Fleck: Is it just me, or is it getting crazier out there?
Arthur Fleck: I used to think that my life was a tragedy, but now I realise, it's a fucking comedy.
Thomas Wayne: Gotham's lost its way. What kind of coward would do something that cold blooded? Someone who hides behind a mask.
Arthur Fleck: What do you get when you cross a mentally ill loner with a society that abandons him and treats him like trash? You get what you fuckin' deserve.
Arthur Fleck: You don't listen, do you? You just ask the same questions every week. "How's you job?" "Are you having any negative thoughts?" All I have are negative thoughts.
Arthur Fleck: I don't want you worrying about money mom, or me.
Arthur Fleck: She always tells me to smile, and put on a happy face.
Sophie Dumond: You're so funny, Arthur.
Arthur Fleck: You get what you fucking deserve.
Arthur Fleck: Everybody's telling me my stand-ups, are ready for the big clubs.
Murray Franklin: All that sacrifice, she must love you very much.
Arthur Fleck: For my whole life, I didn't know if I even really existed. But I do, and people are starting to notice.
Answer: This is later, as the building appears to be Arkham. He's committed there instead of going to jail based on his insanity. It appears he is laughing about the death of Thomas Wayne, we see a flash of that scene again for a reason.
lionhead