'Iron Man 3': The 'Top-Secret' Story Behind Mark Ruffalo's Cameo

'No one could know who Robert was working with that day,' the Hulk himself tells MTV News of teaming with Robert Downey Jr.

As with all of Marvel's movies, "Iron Man 3" ended with an Easter egg — this time, a little button of a scene between Tony Stark (Robert Downey Jr.) and a decidedly unengaged Bruce Banner (Mark Ruffalo), as the eponymous superhero recounts his post-"Avengers" experiences.

According to Mark Ruffalo, that scene was conceived and abandoned at least once before time actually came to film it.

"There was some talk of it, and then I heard we weren't going to do it," Ruffalo told MTV News while promoting "Now You See Me" in New Orleans. "But then I saw Robert at the Academy Awards, and he pulled me aside and said, 'Hey, I have this idea. What do you think?' "

Ruffalo, who has praised his Marvel experience effusively since taking the role of Banner/ the Hulk in "The Avengers," said he was forced to engage in some subterfuge with the press in order to shoot the scene.

"We snuck downtown to a location and shot with [director] Shane Black and had a couple of pages," he explained. "We riffed with it a little bit and shot it, and I snuck out. I remember [I] picked up a paparazzi, and my driver had to drive into the Paramount lot to lose him. And I was laying in the back, and it was just top-secret — no one could know who Robert was working with that day."

When asked if audiences might get to see him again as either Banner or Hulk before "The Avengers 2," Ruffalo said he was unaware whether there were any plans to bring him back to the silver screen. "Not that I know of, yet. But I'm really looking forward to what Mr. Whedon comes up with next," he said of "Avengers" director Joss Whedon. "He's such a bright and teeming creative guy."

"Now You See Me" opens in theaters nationwide May 31.

Check out everything we've got on "Iron Man 3."