|Scarlett Johansson and Robert Downey Jr.stars of "Avengers Assemble"|
When asked what his opinions of his fellow Avengers are, he replied: "I feel like a big brother to Scarlett and Chris Hemsworth has the whole package.
"Jeremy Renner is a serious actor who doesn't take himself seriously at all."
Robert is reprising his role of Tony Stark and his alter ego Iron Man - who he played in the 2008 movie of the same name and its 2010 sequel - in the forthcoming film, which is written and directed by Joss Whedon, but he had concerns about doing it without his 'Iron Man' helmer Jon Favreau.
He added: "He's like a brother. You don't know whether you can't live without him or you want to strangle him in his sleep. I just love the guy."
But the 'Tropic Thunder' star admits Joss was a "perfect" writer and director for the movie.
He explained to Total Film magazine: "He was perfect. During a scene I could say, 'Is this right?' Ten minutes later he had three pages of options for me to try."
Here's the trailer for "Avengers Assemble":