"I want to rip its wings off and fasten a blanket and sleep with it forever," the Oscar winner bizarrely added of his partner Rooney.
During an acceptance speech for the TIFF Tribute Actor Award, the "Joker" star credited his older sibling for his film career and revealed he was "indebted to him for that because acting has given me such an incredible life."
And Mara, who starred in 2011's "The Girl With The Dragon Tattoo", received a special shout out in the audience as Phoenix ended his oration by claiming "Somewhere here, I don’t know where, is a filthy dragon, and I want to rip its wings off and fasten a blanket and sleep with it forever."
Earlier in the speech, after being introduced to the stage by Willem Dafoe at the annual festival, Phoenix paid homage to his legendary brother.
"When I was 15 or 16 my brother River [Phoenix] came home from work and he had a VHS copy of a movie called ‘Raging Bull’ and he sat me down and made me watch it. And the next day he woke me up, and he made me watch it again. And he said, 'You’re going to start acting again, this is what you’re going to do.'"
Phoenix went on to say "He didn't ask me, he told me."
River Phoenix starred in such classics as "Stand By Me", "My Own Private Idaho" and blockbusters like "Indiana Jones And The Last Crusade". He died in 1993 at the age of 23 after a drug overdose outside of The Viper Room in Los Angeles.
At the TIFF gala, his younger brother paid tribute to other members of the Phoenix family as well.
"I feel overwhelmed with emotion, because I’m just thinking about all the people that had such a profound influence on me," Phoenix professed.
"When I was watching those clips, I thought about my family. My sisters Rain and Liberty and Summer, who are still my bests friends."
Meanwhile, Phoenix and Mara have been romantically linked since they worked together on "Mary Magdalene" in 2016. They made their red carpet debut as a couple in May 2017 at Cannes Film Festival.
And in July, the couple appeared to confirm their engagement as Mara stepped out with a huge diamond ring.
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