As Mark Ruffalo continues his press tour for the upcoming indie drama Begin Again, more details are begining to surfacing about Avengers: Age of Ultron, which is currently in production. He once again teases the tantalizing possibility of a stand-alone Hulk movie, as well as whom he'd like to see portray She-Hulk.

Following 2003's Hulk and 2008's The Incredible Hulk, fans finally got the Green Goliath they deserved with Mark Ruffalo's beloved performance in 2012's Marvel's The Avengers. While he is not the only Avenger who hasn't had his own stand-alone movie (Scarlett Johansson's Black Widow and Jeremy Renner's Hawkeye), Marvel fans have been quite vocal about their desire to see Hulk's solo big screen adventure.

Earlier this month, Mark Ruffalo teased that Marvel Studios is finally considering a Hulk stand-alone project, but he also said yesterday that he isn't interested in making Planet Hulk, where Bruce Banner would be practically cut out of the picture.

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In a new interview with IndieWire, Mark Ruffalo acknowledges that the Hulk story is "a tough nut to crack," but reveals that director Joss Whedon's Avengers: Age of Ultron sets up an interesting relationship between Bruce and his massive green alter-ego.

"If we could find a story that's compelling enough to hold people's interest for the two hours -- that is essential. It's a tough nut to crack and I see it as a tough nut to crack. I think it's tougher than the other superheroes because you have a guy who essentially doesn't want to be there doing the thing that you want him to do more than anything. So it can be frustrating as an audience member. It could become a little mirthless. I think that Joss [Whedon] is trying to set it up enough so that we can strike out new ground on that relationship. With the new technology there's a lot to do in Hulk-land that we haven't done yet that is really exciting. So you could have a balance of the two. And I've been finding this relationship between Banner and the Hulk and Hulk and Banner is equally compelling -- it's been explored in the comics, but never in the movies. It's always been Banner's relationship to this sort of lump, this unknowable very two-dimensional thing. But there's also something really interesting about Hulk's relationship with Banner. The only thing that scares Hulk is Banner. It's not some bigger, scarier, huger thing -- it's this frail man. And it terrifies him and it angers him. It's such an interesting relationship that no one has cracked. I feel like that would be an interesting place for us to go. That might hold people's attention."

The actor also took part in his first Reddit AMA yesterday, where he was asked which actress he would like to see portray She-Hulk.

"Oh wow, that's pretty crazy. Well I think Zoe Saldana would be a great She Hulk. It'd be nice to see someone like her join the Avengers. Or someone quiet and demure like Emma Stone would be nice. But it would be up to the powers that be."

Of course, Zoe Saldana is already a part of the Marvel Cinematic Universe, playing Gamora in Guardians of the Galaxy, so it seems highly-unlikely that she could play She-Hulk. Especially considering that she also has green skin in that movie. Emma Stone is coming off of The Amazing Spider-Man 2, where her character Gwen Stacy is killed off, so it's possible that she could jump from Sony's franchise to the Marvel Studios side. But its doubtful we'll even ever see the charcater on the big screen.

When asked if he has a better relationship with Robert Downey Jr. than Bruce Banner does with his "Science Bros" partner Tony Stark in the movies, Mark Ruffalo had this to say.

"Better. We have a really good friendship. We've known each other since before Zodiac. And he's kind of like an older brother that I wish I had. He sort of looks out for me, and I remember when the role came up in the movie, I reached out to him, I was nervous about it, I said 'I don't know if I can do this' and he said 'It's alright buddy, I gotcha.'"

The actor also says that Hulk was his favorite superhero growing up, thanks to Bill Bixby's The Incredible Hulk TV series, but as he became older, Wolverine became his favorite.

"Well, growing up, when I was little it was the Hulk and Bill Bixby's The Incredible Hulk TV show. But as I got older it was Wolverine, and I have a signed first edition of the Wolverine by Frank Miller. That's pretty cool."

CLICK HERE to check out Mark Ruffalo's full Reddit AMA, where he reveals which Pokemon character is his favorite, what makes him "Hulk-level angry," and his favorite Avenger aside from Hulk.