Robert De Niro "really loved" 'The Joker' script.
The Hollywood veteran plays talk show host Murray Franklin in the upcoming movie based on the DC Comics villain (Joaquin Phoenix) - which doubles up as an origin movie - and director Todd Phillips has revealed the 'Meet the Fockers' star was impressed by his and Scott Silver's screenplay.
Todd told Empire "Bob really loved the script. I met with him and said, 'I'd be lying to you if I said we weren't influenced by a lot of your movies.'
"I talked with him about 'Taxi Driver' and about 'The King Of Comedy', which is one of my favourite movies of all time."
According to Zazie Beetz - who plays Sophie Dumond - the film was re-written as they filmed the scenes.
She said: "We rewrote the whole thing while we were shooting it.
Literally, we would go into Todd [Phillips]' trailer and then write the scene for the night and then do it."
Meanwhile, Joaquin previously explained that the crime film will be unlike many earlier comic book flicks as it won't seamlessly fit into a particular genre.
He revealed: "I wouldn't quite classify this as like any genre.
"I wouldn't say it's a superhero movie, or a studio movie or a ... It feels unique, and I think more then anything, and probably the most important thing, is Todd seems very passionate about it and very giving, and so that's exciting.
"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.
"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. And so I think that's what Todd sees appealing about this idea."
The cast also features Douglas Hodge as Batman's future butler Alfred Pennyworth and the likes of Shea Whigham and Billy Camp also make up the cast for the highly-anticipated movie.