I don't really know much about the movie business, but my understanding is that new companies are incorporated for each individual movie project. The investors

I don't really know much about the movie business, but my understanding is that new companies are incorporated for each individual movie project. The investors (of cash, franchise IP, or time) receive shares in that movie's corporation. Presumably the profits are then paid out as dividends, or the company is dissolved, and assets are distributed. That would explain why George Lucas never suffered any dilution on Lucasfilm, which presumably is just a shell whose main purpose is ownership of the various franchises and holding shares in the various sub-companies.