So the first thing he did was zap himself onto the set and take the place of Harrison Ford as Han Solo.
Lucas didn't think he had the right look. Solo was supposed to be this "Dashing, cool-under-pressure" kind of guy. TTWB turned him into some sort of "Asshole rookie cop with low self esteem who ends up getting shot because he keeps harassing minorities"...kind of guy.
So Lucas decided to cut TTWB as solo and tried to use his natural "hateability" in a role more suited to his style.
But that didn't work either when test audiences said The Emperor was way too ugly. Desperate to get rid of TTWB, Lucas decided to play a prank on him and cast him as Queen Amidala. The rest of the cast and crew all had a huge laugh. They staged a photoshoot for this fake movie poster, then kicked him off the set.
