Complex sentence: The story originated with Lasseter wondering what a toy would find upsetting, how a toy would feel if they were not played with by a child or, worse, a child growing out of a toy.
Split into simpler sentences: The story originated with Lasseter pondering what a toy would find upsetting. Lasseter wondered how a toy would feel if they were not played with by a child or, worse, a child growing out of a toy.