Sylvester Stallone will be a part of James Gunn’s “Guardians of the Galaxy Vol. 2.” The director has decided to keep details about his role completely under wraps, but fans expressed their need to know more about Stallone’s involvement.

Finally, due to some prodding by Entertainment Weekly, Gunn gave in a little and revealed some tidbits about his role. “Sylvester Stallone plays a character from the comics who’s an important cosmic character,” he said. “He plays an important role in Yondu’s life. And with him is Michael Rosenbaum, my old buddy, who was on Smallville for many years.”

READ: Chris Pratt believes “Guardians of the Galaxy Vol. 2” will be the greatest movie in history

As amazing as it was to work with Stallone, Gunn admitted that he felt intimidated by the action star. He grew up watching Stallone’s movies and loved pretending he was one of his characters, from Snake Plissken to Johnny Rambo. “Those were my heroes as a child. So, all of a sudden, having to direct Kurt Russell and Sylvester Stallone in a movie is quite an amazing experience,” he said.

He got to address Russell as “Kurt” over the many months they were making the film, and his iconic status wore off a little. But Stallone is different. “With Sly, he’s still Sly. But he’s an incredibly funny human being, and we laugh a lot, and we laugh hard, and he’s also an incredibly professional guy, and we seemed to be very much in synch in terms of how we saw the character, how we saw the scene going,” Gunn shared.

Earlier, Gunn shared some details with Complex about Russell’s character. In the trailer, it was revealed that he plays Ego, the father of Chris Pratt’s Star-Lord. But who is he exactly?

“Ego is a living planet who is able to manifest himself in different ways he’s been alone for millions of years and he's learned how to control the molecules around him in such a way as to create avatars of themselves, such as Kurt Russell,” Gunn said. “I think Ego was a very lonely character out there by himself and went off in search of love and perhaps found it in Quill’s mother.”

Guardians of the Galaxy Vol. 2 hits theaters on May 5.

Sylvester Stallone
Sylvester Stallone has an important role in “Guardians of the Galaxy Vol. 2.” In this photo, the actor poses at the Los Angeles County Museum of Art (LACMA) Art+Film Gala in Los Angeles on Oct. 29, 2016. Reuters/Danny Moloshok