'Iron Man 3': Mark Ruffalo spoils surprise scene on Twitter

avengers-mark-ruffalo-robert-downey-jr-bruce-banner-tony-stark-marvel.jpg "Iron Man 3" is the latest test case for how difficult it is to know the proper statute of limitations on spoilers these days, and "The Avengers" star Mark Ruffalo may have innocently stepped over the line on the movie's opening day.

Warning: If you can't tell already, this post involves "Iron Man 3" spoilers. If you don't want to know any (even tiny ones) stop reading.

Ruffalo tweeted yesterday: "Thank you all for the kind words about IM3. Had a great time cooking that up with Shane [Black] and Robert [Downey Jr.]. Best to all." Which is a lovely sentiment and typical of Ruffalo's upbeat persona.

The only problem: Even though various film sites started to let the secret slip once the movie hit theaters, it wasn't common knowledge that Ruffalo -- who played Dr. Bruce Banner and his alter ego the Incredible Hulk in mega-hit "Avengers" -- actually appears in "Iron Man 3." (The picture above is from "Avengers," not "Iron Man 3.")

There had been some speculation early on that Ruffalo could be a full-on co-star, given the bromantic chemistry between Banner and Robert Downey Jr.'s Tony Stark in "Avengers," but Marvel's President of Production Kevin Feige explicitly denied that the Hulk would appear in "Iron Man 3."

That's true, technically, because Ruffalo makes his "surprise" post-credits cameo as Banner. It's common for Marvel to include post-credits "Easter eggs" in their films -- often teasing a future movie in the franchise -- but this one simply returns to that special connection between Banner and Stark.

The brief scene opens with Stark is sitting on a psychiatrist's couch relating his story. When the camera pulls back we see Banner falling asleep. Stark yells at him to wake up and Banner replies, "You know, I'm not that kind of doctor."

It's the cherry on top of what might be one of the wittiest superhero movies ever made, and Feige tells Collider it was Downey's idea: "We had an idea of that particular Easter egg, but frankly, hadn't cracked it. Mr. Downey helped us crack it."

And now, the secret is out.
Photo/Video credit: Disney / Marvel