I made a quick 3D model of the dick and balls in Blender, animated a first rough pass that would line up with the body, weight painted the base (otherwise the entire thing would just fall down), applied softbody physics to make them jiggle (the dick is partially hand-animated because it didn't jiggle enough at first), added hair on the balls, and simulated those with the built-in hair dynamics. I applied a bit of subsurface scattering on the skin materials to make them look more realistic, set the motion blur to something high like 0.7 (because Illumination always uses a lot of motion blur) and rendered them to a transparent series of EXR images. Then I added the image sequence onto the original footage, rotoscoped the tail so it would still be in front, and rendered that.