Mark Ruffalo's 'Iron Man 3' Cameo Explained By Dr. Bruce Banner

When the cast of "Marvel 's The Avengers" got together to present at the 85th annual Academy Awards, it wasn't just to crack one-liners about Robert Downey Jr.'s height . This year's Oscars ceremony also gave Downey the chance to recruit one of his super friends to make an appearance in "Iron Man 3."

Warning: Spoilers about "Iron Man 3" are ahead.

After the credits at the end of "Iron Man 3," it's revealed that Downey's voice over throughout the film is actually an impromptu therapy session between his Tony Stark and a sleeping Dr. Bruce Banner (Mark Ruffalo). It's an amusing button on the subversive Shane Black film, another moment of levity that undercuts traditional superhero movie expectations. (For instance, Ruffalo's Banner doesn't transform into his alter ego, The Hulk.)

"There was some talk about [an appearance], but when we presented at the Academy Awards, Robert pulled me aside and pitched it to me," Ruffalo, who stars in the upcoming thriller "Now You See Me," told HuffPost Entertainment on Saturday. "They asked if I wanted to do it, I said, 'That's sounds great. I love the idea. I'd love to do it!'"

As Ruffalo recently noted on Twitter , he, Downey and Black worked on the circumstances of Banner's "Iron Man 3" appearance together.

"It was a blast," Ruffalo told HuffPost. "I was so excited to be in an 'Iron Man' movie."

Not that he's gotten to experience that thrill in a movie theater.

"No, I haven't!" Ruffalo exclaimed when asked if he had seen the blockbuster film, which has already earned nearly $1 billion worldwide . "I was there when we shot it, but I haven't even gotten to see [my] scene yet."

"Iron Man 3" is out in theaters now. "Now You See Me" arrives on May 31. Check back to HuffPost Entertainment closer to that film's release for a full interview with Ruffalo.