It was a Danish porn star, named Elvira Friis, who was the body double for Charlotte Gainsburg in this scene. Apparently, the producer/director wanted her to do her own, “ahem”, stunt, but I guess Charlotte’s poor little pooper just wasn’t up to the task. Probably a good move on her part, seeing the reaming and pounding that Elvira’s fart hole had to endure. I like how the dude with the bigger duck was chosen to do the back door exploration. Lol, I have difficulty watching this scene without making audible farting noises!🤣🖤♠️🤎