When a movie like Star Wars is copyright, what exactly does that the copyright protect?
Obviously not the general plot because you have so many (not necessarily Star Wars) movies or books which share a very similar plot line.
What about characters within the movie? I heard rumors that J. K. Rowling wanted to kill off the main characters in her Harry Potter series to prevent them from being used in other works. This would tend to indicate that the characters themselves are not covered by the novels' copyrights. I know movies like Star Wars have a lot of fan fiction including fan made videos which typically do not include the characters from the main movies but I am guessing this has more to do with the difficulty of re-creating the original characters as opposed to creating new ones.
I just posted a fairly authentic rendition of R2D2 in my Reallusion market place store. My R2D2 prop has been made 100% from scratch, by me, but based on images from the movie. I doubt that George Lucas is going to be chasing me down any time soon but theoretically if I am selling my R2D2 on Reallusion's market place then I am gaining from George Lucas' design (of R2D2). Would movies' copyrights extend to the design of R2D2? If so, to what extent? For example, there are a number of other R2 units in the movies. Would this mean that all R2 units are copyright? Anything looking even somewhat like R2D2 could fall in this category.
Hence, my question as to what the copyright of a movie (or novel) actually protects. 


"We often compare ourselves to the U.S. and often they come out the best, but they only have the right to bear arms while we have the right to bare breasts"
Bowser and Blue, Busting The Breast