The reason you want to incorporate is for your own protection. If someone brings a lawsuit against you, they sue the company. If you create something as yourself and an established entity or their lawyers feel you have infringed on their work they can sue you personally. And they will most likely win because they have more resources if it goes to court. If you're under 18 they can sue your parents.
The problem with art is you can both copyright AND Trademark a character, likeness, mannerisms etc. and infringing on something like that opens you up to all sorts of litigation.
Trademarks are hard to get. If you have your own character you want to animate first do research and try and see if anything like that exists in the world. If it does try and change your idea to be as different as possible. Then print out the design, write up the characteristics and also print that out, and at the very least mail it to yourself and dont open it.
If you ever have to go to court you can hand that over in your defense to show how long youve been using said character.
Copyrights are easier to obtain. There are countless resources online on how to go about obtaining one.
One place you do have more freedom is under satire. You can satirize something and be protected. Just look at Don Markstein's Mickey Rat as an example.
