Guardians of the Galaxy director James Gunn took to his Facebook page to share a behind-the-scenes photo from the set, with the filmmaker working alongside his brother, Sean Gunn. We reported in February that Sean Gunn portrayed Rocket Raccoon as an on-set reference through motion capture technology during principal photography, with Bradley Cooper later coming in to provide the voice and perform his own motion capture scenes. However, James Gunn revealed in the accompanying caption with this new photo that his brother also stood in for a very important villain on the set, along with several other characters. Take a look at the image, then read on to see what he had to say.

<strong><em>Guardians of the Galaxy</em></strong> James Gunn and Sean Gunn Photo
"Working with my brother Sean Gunn on Guardians of the Galaxy. This photo is from Sci-Fi magazine which features a great article on how we work together and what Sean contributed to the character of Rocket and to the movie as a whole. It also reveals that, in addition to being the onset Rocket, and using a lot of his body and facial work in the character, he was also the onset Thanos, as well as playing the role of Kraglin, Yondu Udonta's First Mate in the Ravagers, and Peter Quill's lifelong frenemy. Few things in my career give me more creative pleasure than working with my brother."

The filmmaker also answered a few more questions from fans on the comments section of his Facebook post. One fan asked why the filmmaker didn't use a "little person" to stand in for Rocket on the set, instead of his brother. Here's what James Gunn had to say.

"We also had a little person, who we used for reference and lighting in scenes - the very very awesome Arti Shah. But Sean is VERY limber and able to crawl around on all fours at the proper height (Rocket is actually smaller than almost all little people). But what was really important was Sean's acting. He essentially co-created the character of Rocket, and his acting is used throughout the film. It was also of great benefit to the other actors, who had a full scene partner who was as an accomplished actor as all of them. If you read the Sci-Fi article you'll find out from Zoe Saldana how important Sean was to the whole process and her personally. And I know Chris Pratt and Dave Bautista (Batista) also agree. Bautista and Sean had - and continue to have - a special bond that I think is very reflective of the onscreen bond between Rocket and Drax."

When asked who stood in for Groot on the set, James Gunn had this to say.

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"A great Polish fellow by the name of Christian stood in for Groot. He was a mime. But it wasn't quite the same as Sean and Rocket as we didn't use Christian's acting when doing the CGI of the character. Nor does he speak much (obviously) so his interaction with the others wasn't quite the same."