Arguments between friends can capsize a partnership, and The Avengers 2 will prove this in grand fashion as Tony Stark takes on Bruce Banner.

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The upcoming scrape between Hulk (Mark Ruffalo) and Iron Man (Robert Downey Jr.) has been highly publicized, but the reasons behind their very public brawl remain a mystery. With the Age of Ultron trailer now playing across the Internet, Downey and Ruffalo have dropped a few hints about their characters' impending disaster.

"It can't just be a good fight, it's gotta be about something," Downey said at the 2014 San Diego Comic-Con, according to HitFix. "And the great thing in Age of Ultron is, that fight between [the Hulk and Tony Stark] is, nobody wins when two people who are friends fight."

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Ruffalo was even more enigmatic about the pair's seeming falling out, telling HitFix that the reasons for the Hulkbuster scene will definitely be "a surprise."

However, being part of a team is unusual for Banner, and Ruffalo cryptically wondered how long it will last.

"He's trying to really be a part of something and feels more comfortable with the fantasy that he could actually be a part of something," Ruffalo said, according to HitFix. "I still think it's a struggle for him and I never think that he quite has it under control. I think in this, he's as close to having a normal life as he possibly could, which might include some romance. Um, but, uh, uh, you know... is that ever possible for Banner really is the question."

Find out more when Avengers: Age of Ultron hits theaters on May 1. Click the video below to the film's first trailer.