When he first thought about taking on Marvel's little-known Guardians of the Galaxy, writer-director James Gunn's only plan was to breathe life back into the sci-fi genre, which he thought had become drab and grey since the days of Star Wars and Flash Gordon. "I saw it as an opportunity," he says. "I could truly fill a hole of what was missing."

James Gunn at the premiere of Guardians Of The Galaxy Vol. 2James Gunn at the premiere of Guardians Of The Galaxy Vol. 2

Indeed, the original 2014 film was a huge hit with fans, who have returned for the Vol. 2 in record numbers. Of course, most sequels are daunting for filmmakers who are trying to equal the success of the original, but Gunn saw it as an opportunity. "The only restrictions this time were things that we set up in the last movie," he says. "Other than that, it could go anywhere we wanted it to. I got to start from scratch with the story this time. The emotional and action plots were completely intertwined, and all organic and one thing."

Gunn acknowledges that Guardians is an unusual franchise. "It's a rather outlandish concept: a talking raccoon, a bunch of space aliens, one character who's from Earth but has been in outer space for nearly 25 years," he laughs. "I like those guys a lot!"

More: Watch interviews with The Guardians lead cast

And now he's helping directors Joe and Anthony Russo incorporate the Guardians into next year's Avengers movie, Infinity War. "We're always dealing with it, but it is a letting-go process," Gunn admits about watching other filmmakers work with his beloved characters. "Part of it is about what will be best for Guardians of the Galaxy Vol. 3 and beyond, in terms of where they should go. But it's also about making myself of use to the Russos and really focusing on what doesn't have to do with my ego. It's about what's best for those characters."

Gunn admits that he was reluctant to take on making Vol. 3. "It took a long time to decide to do it," he says. "I didn't see much else in life besides Vol. 2 for the past three years. So I needed to be sure that I felt that there was a story that needed to be told. And that I wasn't just doing it for money. And that I wasn't just doing it because the fear of being left out. But I have a story of a raccoon I need to tell right now. Nothing else really appeals to me. I love the raccoon as much as I love my family members."

Watch the trailer and clips from Guardians Vol. 2