While 'Joker' received the most complaints in 2019, its total number is far less than the amount of complaints 'Red Sparrow' received in 2018.
The 45-year-old actor, who won this year's best actor Oscar for his performance in the movie, revealed that De Niro even called director Todd Phillips to make sure he turns up.
Oscar-winner Phoenix made a moving acceptance speech on Monday where he spoke of the importance of animal rights and against dairy cruelty.
Joaquin Phoenix won the best actor Bafta for 'Joker', and said he felt 'conflicted' receiving the award as so many of his deserving fellow actors didn't have that same privilege.
The Warner Bros. project has become the highest-grossing R-rated movie of all time and has crossed the $1 billion mark at the worldwide box office.
Heath Ledger famously portrayed the DC supervillain in 2008 film directed by Christopher Nolan and won numerous awards, including a posthumous Academy Award, a Golden Globe and a SAG award.
Besides Phoenix, veteran Hollywood star Martin Sheen also turned up for the protest and got arrested by the police.
Phoenix attended the protest, standing alongside Fonda onstage to deliver a speech.
Phoenix is vegan since the age of three and has been a longtime supporter of the animal rights organisation