I think this ultimately is a tricky concept in general. I do think Walt unquestionably deserves credit for Mickey, though I would feel more comfortable with Ub Iwerks and even Lillian getting some credit towards their contributions on the characters. Usually the way I've seen it work is that the person who introduced the personality and/or idea for the character is credited with creating the character. This however can be difficult when the character is in a visual medium like comic books or movies, where the image is possibly even more significant then the personality.
In works of literature like Tom Sawyer or Harry Potter, most would likely state Rowling created Harry Potter and Hogwarts, and Mark Twain created Tom Sawyer. However, I don't think either one of them drew them. They may have described them, in their literary work, but someone technically drew what we often relate to those characters, and structures. For something like Dr. Seuss, he drew and wrote his books, as did Carl Barks with Uncle Scrooge.
Some characters however have evolved through the years, and some of the changes to the character that have seemingly become iconic were added by others, and in no way represents the original character. Do these people deserve credit, as they added something that became a part of the iconic version of the character. I think having the general public realize that there are lots of people involved in the process of creating these characters would be most beneficial. I don't see it as a means though to vilify Walt or others in those sorts of positions, but rather to simply realize others were meaningful and important to the legacy of these characters. People used to attend comic conventions and they'd ask Stan Lee to do a small sketch of Spider-Man for them. Stan Lee didn't draw. The general public has, in their praise of him, gotten so carried away with it though, that they think he did everything, when in fact he just wrote for the characters.
Even with a character like Tinker Bell, as far as I've always heard, Tink never had a body and was simply represented by a light in all previous renditions of Peter Pan. However, Walt Disney changed this. Except, once again it was an animator working for him that changed this. I think Walt had final say as to what the character would look like, and the character would be represented as "Walt Disney's Tinker Bell" even though I have no evidence at all to say that Walt ever even attempted to design or draw Tinker Bell. Tink was designed by Marc Davis, and unless you are majorly into Disney history, that name may not be all that recognizable. Ultimately it was Walt who decided they were even going to make a Peter Pan movie, and likley Walt that thought Tink would have a body, though as I said, I don't think he created her in the routine sense. However, when people buy shirts with Tink on them, they usually aren't buying a shirt to represent her personality or life story. It's often just the visual alone that they are gravitating towards.
Not to quote Obi-Wan Kenobi, but it all depends upon your point of view with these things. Some look at the characters as literary creations, and as such the story is the driving force. Others look at them as visual art, which means the artists deserve more credit and attention. Walt over the course of his career was the overseer of much of what Disney Studios did, and his opinion mattered in terms of getting the go ahead on something or having the artist need to rework something. George Lucas is credited with creating Star Wars, and in turn most of the characters. I'm not sure he designed Darth Vader or any number of the aliens found throughout that galaxy. He may have done preliminary sketches, but someone else refined it.
Often times these artists are working for a larger company, and it's known and understood that anything they create is owned by the company, and the artist agrees to this. Sometimes that's not the case though, and since some of these characters are generating millions of dollars in sales, companies feel a bit sensitive to dishing out long lists of people credited with creating the characters, as then those people would want a cut (though often times it's just the company getting the cut). I'm not saying that's right or wrong, just simply why some companies seemingly drag their feet when giving credit. It's a complicated thing, as with some literary characters, the character can be around for years in the public before a visual image is iconisized with it. The Wizarding World of Happy Potter is at Universal, but the company went out and talked to and got the licensing to use the Warner Bros. visuals for the theme park lands, even though it;s a competitor as they understood that the visuals were important, especially in a theme park setting. So using that as an example, both the author (Rowling) and the visuals from the movies (WB) were important in making the Wizarding World what it needed to be. It's possible that Universal could have gotten the go ahead from Rowling without getting the go ahead from WB (though I'm not certain about this part), which would mean they could use Harry Potter in the theme parks, but couldn't use the exacts visuals from the movies. Much like Marvel Super Hero Island isn't allowed to use the cinematic versions of the Marvel Characters. Anyone can have influence and have a hand in helping to create characters, settings, etc. It's a group effort. With most of the Disney characters, I prefer to look upon it as the Walt Disney Company created them, and not any one person. Usually from what I've heard, Disney would often ask many of the animatiors to attempt a design of a character and he'd pick the best, or use inspiration from vrious of the sketches and combine them into one complete sketch. Using that method, some would have impact on the character even though their design ultimately may have been turned down, but the hairstyle was right. If you really wanted to get nit-picky, the man who told Walt that Oswald the Lucky Rabbit was staying at Universal, had some influence in the creation of Mickey Mouse as it made Walt desperate, and he went back to the drawing board, so to speak. Had Walt retained the rights to Oswald, Mickey may never have existed.
