SAN DIEGO - James Gunn is counting on a small, anthropomorphic mammal to make his next film a success.

"Rocket [Raccoon] is the heart of this movie," Gunn told me following the "surprise" "Guardians of the Galaxy" panel at San Diego Comic-Con on Saturday. "If Rocket doesn't work the movie's not gonna work. If Rocket does work the movie's gonna work. And so for me, the whole time it's been about making something that some people could think of as a cartoon or a ridiculous character into a real creature. If a raccoon really was able to walk and talk and make machines and shoot a gun, how would that really happen? How could that occur? And so for me it's about grounding everything in reality."

Speaking of reality, Gunn is under no illusions regarding the Guardians' relatively obscure place in the Marvel Universe, but he takes heart when considering the film in context of 2008's "Iron Man," which itself featured a rather unheralded protagonist at its center.

"The truth is when 'Iron Man' came out, basically nobody knew who Iron Man was," he noted. "'Iron Man'...they sold 15,000 copies of 'Iron Man' a month. That's not enough to even make the first million dollars or whatever. So it really isn't any different...we are starting the wing of Marvel that is the Marvel Cosmic Cinematic Universe. This is Marvel Cosmic. And we're doing exactly what they did with the first 'Iron Man.'"

To hear more from Gunn - including why he thinks the film is a more "natural fit" for him than anything he's done before - check out the full interview above.

"Guardians of the Galaxy" is slated for release on August 1, 2014.