I thought the first CGI character was the glass window in Sherlock Holmes Jr.

Also, in StarWars (1977) They used computers to add in motion-blur (after chroma keying) and to render some of the planets I think.

Lucas Film then invented an animation program along with edit-droid that Disney bought and later became Pixar, which for some time seperated from Disney and was supported by Steve Jobs as they made little cute animations mainly for advertisements. And then they had to rejoin Disney when they wanted to make Toy Story because they needed a studio to back them up.