Details of the upcoming Avengers sequel Age of Ultron are beginning to trickle out and cast member Mark Ruffalo has given fans the biggest hints yet as to the direction in which Joss Whedon is taking the big-budget movie.

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Shooting on the movie began in South Africa last month, with Ruffalo's character The Hulk very much at the center of things. We know that a giant green Hulk head on a pole was used to terrorize extras - but was Ruffalo out there too?

"The Twitter-verse is all alive with that [question]!" Ruffalo told Vulture at Peggy Siegal's party for the HBO series Doll & Em this week, "I actually already shot a lot of that stuff, we did it on motion capture, so we did a lot of that on a stage. So they're doing all the [background] plates for that now in South Africa, and then I start work in mid-April."

Rumors doing the rounds on Marvel message boards and on Twitter claim Bruce Banner will have a legitimate love interest this time around and Ruffalo gave a "wide grin" when posed the question. "That may or may not be true," he said, coyly.

Elsewere in Avengers land, Marvel have released new concept art for characters Quicksilver and Scarlet Witch - set to be played by Aaron Taylor-Johnson and Elizabeth Olsen in Age of Ultron. 

More: Avengers Age of Ultron to shoot in South Korea.

Kick-Ass 2 actor Johnson told MTV News of the role: "I feel really flattered and honoured that they came to me for that role.

"I sat down with Joss, I think he's awesome, I sat down with the guys at Marvel and they're also great. I think it'd be interesting."

"The thing to think about is he's an abandoned child, him and his sister are abandoned in Eastern Europe."

The Avengers: Age of Ultron is due out on May 1, 2015.

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