10. Up (2009)
While WALL-E represents the end we still don't have a full picture of how it all happened which is where the rest of Pixar's filmography comes in. Starting with Up the animals are gaining more and more information to further use against the humans. The film is the final straw between man and beast that ultimately sets the war into motion. Animals have already been established to be intelligent at this point yet they cannot communicate with the humans and they haven't started their resistance just yet. In Up a harness is developed which allows animals to now talk to humans. This is a major step for the theory. Humans now have the ability to speak to animals so they would go about putting the harness on anything they could which infuriates the animals and causes major strife between the two species.