...on my car? If i wanted to paint a big hello kitty head on my car's hood.. would I need to contact Sanrio or something? Or is that sort of thing free to the public and what not
if you are doing it for commercial gain (ie if the reason for painting your car is to promote your business) you would need to get permission and pay a fee.
Even if it's just for fun, you can't just reproduce someone else's artwork without agreement - it could be breach of copyright. Why don't do paint a cat design of your own creation instead?