I've thought of some more possible rivals for Disney:
- Fleischer Studios: Brothers Max and Dave Fleischer were Disney's main competitors during the early days of animation in the US (barring the Warner Brothers). They gave comic strip characters like Superman and Popeye their own theatrical shorts; they also created their own classic cartoon characters like Betty Boop.
- UPA: You know those cartoons that use limited animation and have thick lines around everything? Well, chances are they were ultimately inspired by cartoons from the relatively obscure United Productions of America, who wanted to create a stylized approach for their animation to contrast with Disney's quasi-realism and WB's surrealism. They created some iconic characters (like Mr. Magoo and Gerald McBoing-Boing) and made well-received adaptations of classic literature (like "The Little Match Girl" and "The Tell-Tale Heart").
- Jiří Trnka: He was a Czech puppet-maker, illustrator, motion-picture animator and film director. He is best known for his work in animation with puppets. Most of his films, usually adaptations of literary works, were intended for adult audiences. However, because of his influence on animation, the man has been called "the Walt Disney of The East" or "the Walt Disney of Eastern Europe." This is sort of like how Hayao Miyazaki and Osamu Tezuka are both contenders for the title of "the Walt Disney of Japan." Speaking of which...
- Osamu Tezuka: Hayao Miyazaki and his associates at Studio Ghibli have crafted several top-grossing internationally-acclaimed animated movies with incredible depth and detail, with memorable characters like Nausicaä, Totoro, Mononoke, Ponyo and Arrietty. Tezuka, however, is considered the grandfather of animé and manga due to his prolific and varied output. He also happened to be inspired by Walt Disney himself, and the two eventually became friends. Not only was Tezuka the one that made Japanese pop-culture icon Astro Boy, but he also produced the first Japanese animated series to be in color, "Kimba the White Lion", which might have been an inspiration for Disney's renaissance-era classic, "The Lion King."