Samuel L. Jackson, right, welcomes Robert Downey Jr. onto the stage during a panel for the movie "The First Avenger" at Comic-Con International Saturday, July 24, 2010 in San Diego.

*The Marvel Studios presentation at Comic-Con Saturday presented surprise guest Samuel L. Jackson to introduce the all-star cast of its forthcoming film “Avengers.”

Just as the company’s panel was winding down, the actor took the stage before some 6,000 fans to bring out stars Clark Gregg, Scarlett Johannson, Chris Hemsworth of “Thor” and Chris Evans of “Captain America.”

He then introduced another surprise guest, Robert Downey Jr., who brought out the rest of the cast, including Jeremy Renner as Hawkeye and Mark Ruffalo as Bruce Banner.

“The Avengers” is based on the comic book series of the same name, which brings various Marvel superheroes together. The film is due in 2012.