Pixar knows this better than anyone -- Finding Nemo isn't really about a fish; it's about parents letting their kids be kids and take risks. Cars is about how the urbanization of America killed its soul. Brave is about the survival of the mother/daughter bond through life changes, and how all little girls are bears at heart. And Toy Story is, inexplicably, about how we all need to cling to the childhood belief that inanimate objects are people. Oh, there are other little messages along the way -- the power of friendship, overcoming obstacles with teamwork, shit like that -- but the overarching theme and moral are just nuts.
Let's briefly recap all three films:
Toy Story: The cowboy doll Woody is jealous when Andy (the boy who owns him) gets a new toy, Buzz Lightyear, because Woody fears that it means Andy's tastes are changing and that he'll get left behind. The villain is Andy's neighbor, Sid, who is evil because he "tortures" his toys -- he pulls them apart and pieces them together to make new toys. That's a crime in this universe, because toys are sentient, and Sid is too stupid to realize it, even though he has never seen any evidence for that fact whatsoever and realizing it would destroy his sanity. Sid is punished for being creative with the toys and using them in a way the manufacturer never intended, while Andy is praised for "correctly" thinking his toys are real and treating them as such.
If Sid learns any lesson, it's "Don't tell adults about traumatic events because no one will believe you."
Toy Story 2: Woody discovers that Andy has been discarding broken/unwanted toys as he gets older and (again) fears that he will suffer the same fate. Woody then gets a chance to go to a toy museum, where he will live forever behind glass and never be discarded to a trash dump, but ultimately decides to go back home and hopes that Andy holds onto him as long as possible. The unconscionable horror of throwing away a toy is reinforced in a heartbreaking sequence where another doll, Jessie, talks about how her owner hit puberty and then stuffed her in a box in the dark -- the toy version of hell. The villain of the movie is an evil toy collector who sees toys only as commodities to be bought and sold, rather than sentient beings with the same rights as humans.
"Fuck you for trying to earn a living."