Throughout the whole movie, aspiring comic Arthur seems to truly admire Murray Franklin (Robert De Niro), a Johnny Carson-esque talk-show host with a bit more sleaze. Arthur imagines what it'd be like to be a guest in the audience and tell Murray how much he means to him.
After Arthur's attempt at stand-up — which Arthur seems to think went swimmingly — Murray shows a clip of it on his show, just to make fun of him. He even goes as far as referring to him as "Joker" while picking at how decidedly not funny Arthur is. However, Arthur gets a call soon after inviting him to be a guest on the show.