'Guardians of the Galaxy 2' news: Sylvester Stallone, Michael Rosenbaum join cast

James Gunn has confirmed that Sylvester Stallone and Michael Rosenbaum will be joining the cast of "Guardians of the Galaxy 2." While their roles in the upcoming movie are not revealed yet, speculations are running on who they will be playing, especially after the director hinted that the two will be playing characters who have significant roles in the Marvel universe.

In his interview with Adam Carolla, Gunn said that the two will be working together. This hint has had fans guessing which characters they will be playing in the film, with some guessing that they may be part of the Nova Corps, with Stallone as Jesse Alexander, one of its Centurions, and Rosenbaum as Richard Rider. Another theory is that both will be playing space pirates known as the Ravagers. Some are also proposing that they are the High Evolutionary and Adam Warlock.

Stallone is no stranger to starring in a sci-fi film set in space, having played the titular role of "Judge Dredd." Rosenbaum, meanwhile, is best known for his work in DC Comics' TV adaptations, having played Lex Luthor in "Smallville" and doing voiceover work for some of the comics company's animated series.

Gunn is keeping mum about who these characters are so far, but he is not above to teasing fans about it. In an interview with Yahoo! Movies, he said, "Look for clues and you will find out the character Sylvester Stallone plays."

"He is fantastic in the movie. It's a very important part of the Marvel cosmic universe," he added.

Kurt Russell was previously confirmed as a new cast member of "Guardians of the Galaxy 2" as well. He plays the role of Ego the Living Planet, who is also the father of Peter Quill, also known as Star-Lord (Chris Pratt).

Meanwhile, the IMAX promotional poster of "Guardians of the Galaxy 2" was just released. Gunn uploaded this on his Facebook account, enticing viewers to watch the film on IMAX by saying that every shot for the film was made with 3D in mind.

"Guardians of the Galaxy 2" will premiere on May 9.