Disney and other studios/companies have their own licensing divisions. I don`t know anything about the process but I would assume they have certain standards for products that their characters are put on.
I once came across the a site with character licensing for one of the newspaper syndicates, which owns many comic strips. I suggest searching for a site like it for Disney to see if there is some basic info.
Yep...Disney (and most everyone else) has very strict requirements about the use of their characters. You can find more information about licensing at www.licensing.org. I have lots of experience with licensing so let me know if you have any specific questions.