This actually took quite a bit of consideration to complete, so enjoy my answers.
The Little Mermaid: a character who is out of their element, a "fish out of water"
There are many characters that qualify for this category, but Genly Ai, from Left Hand of Darkness, is a favorite of mine. A human envoy from an intergalactic coalition of planets (the Ekumen), he is sent to the planet Gethen to encourage them to align themselves with the Ekumen. Besides the culture shock of being on a different planet amongst alien life, Genly also has to come to terms with the ambiguous sexuality of a race that routinely changes gender.
Cinderella: a character who goes through a major transformation
A manga that I haven't seen enough people discussing is Koe No Katachi, or A Silent Voice. The main character, Shouya Ishida, begins the series as an ignorant oppressor of a fellow student who is hearing impaired, harassing her so completely that she moves. Later, through his own experience as a victim of bullying, he learns to empathize with her and feels convicted; therefore, he sets out to find her and redeem himself.
Snow White: a book with an eclectic cast of characters
Les Miserables has quite the diverse cast. Though not racially varied, the characters differ politically, economically, and socially, as well as by age, gender, and backstory.
Sleeping Beauty: a book that put you to sleep
Rarely do I put books down without finishing them, but I couldn't endure China Boy any longer. The plot seemed to never advance, which I don't typically mind in character-driven novels. However, none of the players grew either. I read half of the book, and it lacked focus and development, absolutely boring me.
The Lion King: a character who had something traumatic happen to them in childhood
Batman is one of my favorite characters of all time, and obviously fits this category. As a child, Bruce Wayne witnessed his parents get gunned down while out with them one night. Their murder served as the catalyst for his taking on the vigilante mantle of Batman.
Beauty and the Beast: a beast of a book that you were intimidated by but found the story to be beautiful
The Sound and the Fury is not tome, but its style and reputation did well to dismay me when I approached it. However, once I started it, I saw that, though difficult, it wasn't insurmountable. Moreover, the unorthodox structure added to this tragically beautiful classic.
Aladdin: a character who gets their wish granted, for better or for worse
Out of all the characters I could list, Draco Malfoy is my favorite. From the beginning, he wished for the same attention and fame as Harry. In The Half-Blood Prince, his request was granted when Voldemort inducted him into the Death Eaters and gave him the mission of killing Dumbledore. He very quickly realized, however, that this wasn't the recognition he dreamt.
Mulan: a character who pretends to be someone or something they are not
Tess from Tess of the d'Urbervilles is the most tragic example I could think of. She pretends to be from a different family and of a different class, and then she lies to cover up her past shame. Of course, neither farce works for her better, and she ultimately meets a heartbreaking end.
Toy Story: a book with characters you wish would come to life
There are so many characters I wish were real. Obviously, I would love to befriend The Golden Trio from Harry Potter. I would be equally happy with the Marauders.
Disney Descendants: your favourite villain or morally ambiguous character
Often times, I find the antagonist of a story more compelling than the hero. My recent favorite is Scott Snyder's Joker. Death of the Family cemented him in my top ten because it's one of the few I find truly unsettling.
And that is the Disney Book Tag. What do you think of my answers? Do you agree, or would you have chosen different answers?
Since this tag has been going around for awhile, I don't nominate anyone in particular. If you want to do it and haven't yet, you are tagged.