Another thought from Inside Out: Like Toy Story, Monsters Inc. and WALL-E it starts as a workplace comedy for an imaginary job, before taking some characters out of that space on a big journey that will ultimately change the setting substantially. The initial setup could be a series premise in itself, with the journey outside and resulting changes happening several adventures down the line.
The stranger the premise, the more thought would have to be given to the requirements for the job - toys living in secret is relatively easy to work through, but Monsters Inc. gets a huge action scene out of their idea for how monsters get to closets, and Inside Out has a whole lot to connect with thought processes being represented.
See also the more domestic version, as in Finding Nemo or The Incredibles. A Bug’s Life is a classic adventure setup already.
Obviously it also needs some great character design. (Check out Pixar designer Everett Downing’s 365 Supers for superheroes who could easily fill out an animated universe of their own.)
And at least one huge emotional gut-punch.
See also the Pixar 22 rules of storytelling.
I just covered Rule 4: Once upon a time there was ___. Every day, ___. One day ___. Because of that, ___. Because of that, ___. Until finally ___.