what happen between him and lucas was that he made a joke between the first star wars movie and filming empire strikes back that he was lukes father. this was carried in a fan news letter and published right before the release. The actor claims that he said this before he ever got the script and at the time had said a lot of other goblygook in jest to the person who interviewed him. to this day no one but him and the fan who interviewed him knows if it true. George Lucas was stuck using him because of contract and tried to remove all evidence of him being the actor including digitally removing his face and putting another actors face on the body of a dying Vader in the return of the Jedi
my source is a documentary I viewed this year unfortunately cant remember the title
Lucas himselg gave it away. He made tge chadaxter’s name similar to the Indoeropean words for father.