Those reports of Shia LaBeouf putting it in a real girl were all lies. Originally, we were told that Lars von Trier‘s Nymphomaniac would feature its stars (LaBeouf, Uma Thurman, Charlotte Gainsbourg, Stellan Skarsgard) having real onscreen sex instead of just wiggling around awkwardly until they come into a sock. Then, there were reports that the film would employ body doubles and visual effects. However, The Hollywood Reporter has discovered what is actually planned. It does not involve Andy Serkis dressing up in a penis costume, sadly.
Producer Louise Vesth filled in the details. “We shot the actors pretending to have sex and then had the body doubles, who really did have sex, and in post we will digital-impose the two. So above the waist it will be the star and the below the waist it will be the doubles.”
This is easily the most perverse use of Forrest Gump technology.