While Joker director and co-writer Todd Phillips admits his DC film may not be for everyone, it has certainly made a name for itself -- even becoming the first R-rated movie to reach $1 billion at the global box office. Filmmaker Michael Mann -- whose 1995 film Heat was an inspiration for Christopher Nolan's The Dark Knight -- even penned a letter to Phillips and those involved, praising the movie.

Per IndieWire, the letter was read to Phillips by fellow filmmaker Scott Cooper before a Q&A session with Phillips began. Due to a scheduling conflict, however, Mann could not appear to interview Phillips.

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"I love this movie," Mann's said of Joker in his letter. "I think it’s brilliant and not only Todd’s best film but it’s exciting because it’s on a frontier. And that’s usually where very good things happen. Todd and Scott [Silver’s] screenplay has that relevance that occurs when work is authentic and not derivative. We find Arthur [Fleck, the Joker] disturbing and poignant simultaneously. He’s both child victim and adult perpetrator. Both are true, as is the case with most schizophrenics. That both are true is uncomfortable. We find ourselves in a fugue state. It’s counterpoint. It’s why Arthur and the film’s impact sustains so strongly in memory. To build on all of this, and for Joaquin, Todd and Scott, to impact upon on this powerfully is a difficult accomplishment. Congratulations, Todd!"

Phillips was, of course, amazed by this. "That’s amazing to hear a letter from Michael Mann,

Phillips said. "I’m such a huge Michael Mann fan. He knows that, we’ve spoken about it."

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Directed by Todd Phillips, Joker stars Joaquin Phoenix, Robert De Niro, Zazie Beetz, Bill Camp, Frances Conroy, Brett Cullen, Glenn Fleshler, Douglas Hodge, Marc Maron, Josh Pais and Shea Whigham. The film is now in theaters.