Ufortunately, I'm not able to upload a movie clip for you to show, but the segment I want you to check out is from 2:30 to 2:50 in this clip: http://www.youtube.com/watch?v=oEHDA9OyyDU

Watch closely as you will see the back of 3PO's to be strangely "bulgy", mostly near the neck, as is the place where Anthony Daniels' chin protudes (he had 3PO's face behind his own, because Chewbacca screwed the droid's head backwards). It's something that annoyed me every time since I saw this scene for the very first time...

Hope this sheds some more light to it! :)