Sean Gunn at the "AVENGERS End Game" premiere
Sean Gunn Was Surprised By Guardians Of The Galaxy's Massive Success. Of course, Marvel knew better and Guardians of the Galaxy went on to become a major hit, so much so that even those who believed in the project were blown away. Among them was writer-director James Gunn’s brother, Sean Gunn, who plays Kraglin and the on-set Rocket Raccoon in the films. Sean Gunn was surprised by just how massive the first movie's success was, as he explained: