James Gunn has shared a behind-the-scenes video of his brother, Sean, portraying Rocket Raccoon in Marvel Studios’ Avengers: Endgame.

Rocket originally appeared in the first Guardians of the Galaxy film and instantly gained popularity among fans. Fans adored his friendship with the tree humanoid Groot. There were even speculations that Marvel Studios CEO Kevin Feige had been pitched a Groot/Rocket series for Disney’s planned streaming service Disney+. Rocket has appeared in three films after his debut appearance: Guardians of the Galaxy Vol. 2, Avengers: Infinity War, and Avengers: Endgame.

Sean is seen striding beside the Avengers as they stride briskly into their hangar in the footage posted by James. Gunn, on the other hand, is walking in a stooped stance and leaning on his arms for more balance and leverage.

After watching this footage a several times, I believe that every actor in the MCU should be applauded for their efforts in maintaining a straight face while shooting these films. I’m not sure I’d be able to deliver lines alongside Sean Gunn without laughing out loud. I’m not sure how Sean Gunn manages to maintain his composure.

This is @seangunn doing motion reference for Rocket on set in #Endgame. Contrary to popular opinion, he’s not a stand-in as much of Rocket’s acting and facial expressions are Sean’s. And yes it’s hilarious every time. pic.twitter.com/GTRa5RQq9Z

— James Gunn (@JamesGunn) July 30, 2019

Gunn was interviewed by ComicBook.com earlier this year. He mentioned how playing Rocket turned out to be more engaging than he had anticipated. “In the first movie I wore the, you know, whatever you call it, but the nylon onesie,” Gunn explained. “But then in the second movie and in the two Avengers movies, I just wore a gray sweatsuit, which was a lot more comfortable and I wear some knee pads and things like that. The thing that was unusual is that the motion capture part of it, which is technically motion reference, not motion capture because it’s not, they’re not doing it through a computer. The animators are literally watching what I do and animating that rather than sending it through an algorithm the way that you would do it with the way you would do it with a more humanoid character. That doesn’t work for a raccoon. It just doesn’t, the technology isn’t there. It doesn’t look good enough. So the animators actually watch what I do and animate that.

“But that part of that, we didn’t even know that that part was essential when we started it. The main reason that I was there was so that I could read the lines with the other actors and be an actor in the scene with them and I got down low because I knew for sightlines and things like that, that you’d want to be looking at a pair of eyes when you’re looking at the character’s eyes, so we did it like that really for the other actors. It wasn’t until we had been shooting for a week or two that the visual effects team said, ‘You know, these shots that we have of Sean in there are incredibly helpful to us as we start to animate Rocket and we start to know where he’s looking and where his hands are moving and what his, you know, what his shoulders are doing and that kind of thing.’ And so then we started making sure that we got at least one really strong reference shot with me in it for the animators, and then I would step out and do it through the subsequent takes from behind the camera and I’d be just doing my same vocal performance but feeding the actors the lines.”

Sean Gunn did the same for Thanos in Guardians of the Galaxy, in addition to supplying motion references for Rocket. In Guardians of the Galaxy, Guardians of the Galaxy Vol. 2, and Avengers: Endgame, he played the live-action character Kraglin. Kraglin initially appeared in the MCU as a villain and Yondu’s right-hand man. He also provoked a mutiny with Taserface by mistake, but afterwards regretted his actions. After that, he aided the Guardians in their fight against Ego. Kraglin and his fellow Ravagers assist the Avengers in defeating Thanos in Avengers: Endgame.

In James Gunn’s Guardians of the Galaxy Vol. 3, Sean Gunn is likely to reprise his role as Rocket Raccoon. After James Gunn completes his directing responsibilities on Warner Bros. and DC’s The Suicide Squad, production on the picture will commence.