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Big shoes to fill - The Batman universe demands a lot to play the Caped Crusader's arch-nemesis, the Joker, and Phoenix is poised to perhaps surpass Heath Ledger's iconic performance as the Clown Prince of Crime.

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Drastic body transformations - He lost a shocking 52 lbs (23.6 kg) in order to achieve the proper physique for the role, and as he wasn't a heavy guy before, it was surely a daunting task.

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It took a mental toll - He told attendees at a Venice Film Festival press conference about the drastic weight loss, and said, "As it turns out, that impacts your psychology, and you really start to go mad when you lose that much weight in that amount of time."

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He channeled that madness - Phoenix sacrificed his own mental balance to properly embody this unbalanced character, but he has come back from it seemingly healthy.

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He doesn't care about DC fan concerns - When asked if he was worried about letting people down, the actor said, "I could care less. I don't really think that much about what people think. Who cares, who cares? My approach to every movie is the same. What I'm interested in is the filmmaker and the idea of the character." 

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Reclusive star - Phoenix has been in some pretty big films, yet has a history of disappearing from the spotlight.

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Like the Joker, he has experience tanking his career - In 2008, after appearing in the indie 'Two Lovers,' Phoenix announced his official retirement from acting in order to pursue a career in hip-hop. One of his first public appearances post-retirement featured him rapping, very badly, at a Miami nightclub where he fell off the stage. 

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He gave up years of acting to make a point - He also gave a cringeworthy but hilarious interview, on the 'Late Show with David Letterman' in which he looked horrendous and couldn't answer questions coherently. 

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'I'm Still Here' stirred a media frenzy - Casey Affleck (Phoenix's former brother-in-law) directed a documentary called 'I'm Still Here,' charting Phoenix's move from actor to rapper. The 2010 documentary was a concerning vignette of Phoenix's life, trying to get P. Diddy to produce his music, spinning out on drugs, engaging in lewd sexual acts, etc.

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Then came the point - Weeks after the premiere, it was revealed that the documentary was actually a mockumentary, and Phoenix's public appearances in character for two years were all an elaborate hoax designed to criticize the media's desire to cover celebrity breakdowns.

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He had an unusual upbringing - Phoenix was raised in the extremely controversial Christian cult, Children of God. It's reported that he and his family used to travel across South America sharing their beliefs.

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His parents changed their name after leaving the cult - After leaving Children of God, his parents changed their family name from Bottom to Phoenix, symbolizing their rise from the ashes. "Cults rarely advertise themselves as such," he said in a 2014 interview with Playboy. "It's usually someone saying, 'We're like-minded people. This is a community,' but I think the moment my parents realized there was something more to it, they got out."

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He called 911 when his brother overdosed - Phoenix was at the same nightclub when his brother River died from a drug overdose in 1993. River, a talented 23-year-old actor, had taken to using a cocktail of crack, coke, and heroin. On that tragic night, a 19-year-old Joaquin placed the call.

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River was the reason he kept at acting - While accepting his TIFF Tribute Actor award, Phoenix thanked his late brother, recalling a time when River had come home with 'Raging Bull' and made him watch it twice, telling his younger brother to keep acting.

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Werner Herzog may have saved his life - In 2006, the actor overturned his car while driving in Hollywood. Legendary filmmaker Werner Herzog happened to be driving by and rescued him from the wreckage. "There's something so calming and beautiful about Werner Herzog's voice," Phoenix said. "I felt completely fine and safe."

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Relationship with Rooney Mara - The private actors worked together on the 2013 film 'Her,' where they played divorcees, and they're also in 'Mary Magdalene' together.

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Engaged - After a reported three years of dating, the actress said "yes" to her sometimes costar on July 21, 2019, ET Canada reports.

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He'd never sang before 'Walk the Line' - The 2005 Johnny Cash biopic was perhaps most astonishing during the credits, when everyone realized that it was Phoenix's voice on the soundtrack and not Cash's—and it was his guitar-playing as well! He reportedly surprised himself, along with famed film critic and huge Cash fan Roger Ebert, who wrote that he was "gob-smacked."

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He went method for Cash - In order to fully embody the hard-drinking musician, Phoenix opted to go method, staying in character all the time. He even asked everyone on set to call him, "J.R." which was Cash's real name. He later explained, "I use all the help I can get."

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He still experiences anxiety about acting - Despite having over three decades of experience, Phoenix still gets anxious on a movie set. "I still get nauseous the day before and have weeks of incredible anxiety," he told Interview Magazine in 2012.

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He still experiences anxiety about acting - Despite the fact that he said "They have to put f**king pads in my armpits because I sweat so much that it just drips down my wardrobe," he also really enjoys the anxiety, "I love it."

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His acting technique is opposite - While many actors spend a lot of time learning their lines, following their light, and hitting their marks, Phoenix told Interview, "You should not learn your lines, you should not hit your mark, and you should never follow your light. Find your light—that's my opinion."

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He went by the name Leaf for over 10 years - In 1978, Phoenix changed his name to Leaf because he was irritated that people couldn't pronounce Joaquin properly. His four siblings also all had nature-related names.

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He was about four years old when he changed it - "I used to get really embarrassed about it as a kid. All kids in my family had gorgeous names and I got 'Joaquin.' I said 'This is not good.' Even I can't say it." He kept the name Leaf until 1991, after filming 'Walking the Dog.' It was also during that time that he took a break from acting.

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He's been vegan since the age of three - Phoenix decided to be vegan in his early childhood after witnessing a fisherman brutally killing his catch. He told Playboy that he avoids leather in his real life, but makes concessions for films with budget constraints.

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He was home-schooled - Phoenix started acting regularly at the age of six, and was home-schooled when he wasn't being tutored on set. He told Playboy he regrets not giving education his all: "You get old enough and realize there was plenty of time to invest yourself in several things."

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He went to rehab for alcohol abuse - Phoenix had entered rehab for alcohol abuse about five months before an interview with The New York Times in 2005, in which he sounded healthy and said "There is no finish line with this. I don't think I'll ever know if I succeed. But that's OK - it makes you work harder."

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No pictures with fans - It's not that he's a bitter star who doesn't appreciate his fans, but Phoenix told Playboy he much prefers having a conversation with people.

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He's not a fan of acting awards - While he's been given many trophies in his career, he once compared award shows to a terrible tasting carrot: "I think it's total, utter bulls**t, and I don't want to be a part of it ... It's a carrot, but it's the worst-tasting carrot I've ever tasted in my whole life. I don't want this carrot."

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He's already generating Oscar buzz -

While he may not be a fan of awards, people are already counting on at least an Academy Award nod for Phoenix's performance in 'Joker.'

See also: Who is the best Batman of them all?

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