Strangely, Bradley Cooper's biggest role of recent years has turned out to be the voice of the Guardians of the Galaxy series' talking raccoon Rocket.
But the Silver Linings Playbook star doesn't get to don a bright green motion capture suit to represent the character on set.
Director James Gunn was asked during a Facebook Live why his brother, Sean Gunn, is used as a "stand-in" for Rocket instead of Cooper.
"Sean Gunn is not a stand-in," he said (via Heroic Hollywood). "He is a motion reference actor. That means we film everything Sean does on set as Rocket. We film it.
"I don't stop doing takes of him until we get the performance right and then we use that performance as a basis for much of Rocket's acting.
"And he does a fantastic job in that role. He knows it. He understands it. And also very important – Sean is able to physically do something most actors aren't able to do, which is waddle around on all fours.
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"He's always been an incredibly limber guy that can do a lot of strange physical things. And the fact that he's able to waddle around on his legs all day long at the exact height of Rocket is quite a feat and quite difficult."
Sean Gunn doesn't only play Rocket in the films. He will also reprise his role as the Ravagers member Kraglin in Guardians of the Galaxy Vol 2.
Chris Pratt, Zoe Saldana, Dave Bautista, Vin Diesel, Michael Rooker, Karen Gillan, Pom Klementieff, Elizabeth Debicki, Chris Sullivan, Sylvester Stallone and Kurt Russell will also feature in the movie.
Guardians of the Galaxy Vol 2 will be released on April 28 in the UK and May 5 in the US.
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