When Dave Bautista found out he got the role of Drax the Destroyer, he broke down in tears, overjoyed at getting a Marvel comic-book role. He immediately signed up for extra acting classes in order to prepare for the role.
According to Vin Diesel, the voice of Groot, he recorded Groot's iconic line, "I am Groot," over 1,000 times.
The soundtrack album "Awesome Mix, Vol. 1" reached number one on the US Billboard 200 chart, the first film soundtrack ever to reach number one without a single original song.
Director James Gunn didn't want to see Chris Pratt auditioning. He was convinced later by his assistant, at the end of the auditions. After Pratt read for 30 seconds, Gunn stated that then he knew that Pratt was perfect for the role.
Chris Pratt and Dave Bautista spent two and a half months training and rehearsing for their fight scene. On the Friday night before the Monday they were scheduled to film the scene, director James Gunn decided that the fight wouldn't work on camera, so he scrapped the entire fight sequence they had been practicing. Gunn also decided that he wanted the entire fight to be filmed in one long shot with no cuts. As a result, Pratt and Bautista only had a few hours to learn the choreography for the fight sequence that is in the movie. According to Bautista, it took them 22 takes to get it right on film.
Chris Pratt went on a very strict training regimen and diet for 6 months and dropped another 60 pounds eventually getting a six pack for his shirtless scenes. Chris Pratt said that it was a lot of hard work, almost 'torturous', but when he was filming his shirtless scenes and saw the playback on the monitor, he felt the effort was well worth it and he was "extremely excited to see the best possible physical version of himself".
When Vin Diesel started recording his lines for Groot, he was pleasantly surprised to find himself working with an old friend, Doc Kane, the sound technician he'd worked with on Järnjätten (1999).
The Guardians of the Galaxy is primarily based on the 2008 comic team (Star-Lord, Gamora, Drax, Rocket Raccoon and Groot), but features Yondu, a member of the original 1969 comic team, as an ally.
To prepare for the role of Nebula, Karen Gillan shaved her head.
Joel Edgerton, Eddie Redmayne, Jensen Ackles, Lee Pace, Wes Bentley, Jack Huston, Cam Gigandet, Sullivan Stapleton, Logan Marshall-Green, Garrett Hedlund, Chris Lowell, James Marsden, Jim Sturgess, Joseph Gordon-Levitt, Aaron Paul, Michael Rosenbaum, Glenn Howerton and John Krasinski auditioned and screen tested for the role of Peter Quill/Star Lord.