Im not sure if was tom and jerry, it looked older. I havent seen it since I was a kid. It was this grandfather mole or mouse (or some other small mammal) telling his grandkids about these animals called humans. I remember him saying that they had long noses (remarking on their gasmasks) and how violent they were. It ended with the last human being shot and dieing in the mud. Yea I guess they dont show it anymore for obvious reasons. Wish they did though I loved that show.