The flame-shooting guitarist or "Doof Warrior" is Sean Hape, better known as iOTA, an Australian actor/musician who moved out of his home at age 17 to form the hard rock band Loose Goose. According to Hape, the guitar weighed 132 pounds, and shot real gas-powered flames, which he controlled using the whammy bar.
During the filming of Guardians of the Galaxy, Gunn kept a pile of Play-Doh containers on set. If someone did an exceptionally good job that day, whether it was an actor, a grip, a stunt man, or a PA, he would reward them with a canister of Play-Doh. "Who doesn't love playing with Play-Doh?" he said. "I love the smell of Play-Doh; opening a new container and smelling it puts me in a creative, child-like place."