Joaquin Phoenix never officially agreed to star in the 'Joker' movie.

The 45-year-old actor played the titular character in the widely acclaimed movie, but director Todd Phillips has now revealed he wasn't sure of Joaquin's participation until he showed up for wardrobe.

During a roundtable discussion for the Los Angeles Times newspaper, Todd shared: ''If you took two pages of our script and you [hold it up] to our scene, you realise how an additive an actor can be.

''It was a pursuit to get him because initially it feels like, 'ugh, comic book movie.' Just the idea of it is something he wasn't so keen on pursuing, and even when I would explain to him it's not that, it kind of says that, but really we're doing this other thing, there was a little resistance.

''But the more I got to know him, the more I hung out with him, and we spent a lot of time talking about what the movie will look and feel like, and then one day he magically showed up. He never said yes. ''He just one day showed up to a wardrobe fitting. It was an incredible partnership.''

Meanwhile, Todd recently admitted he's in no rush to start work on a 'Joker' sequel.

He added: ''A movie does that kind of business and became that beloved around the world - they had talked to us about it. Joaquin and I had spoken about it anyway as far back as when we were shooting the movie.''