Do you know this animated film? Human pets, aliens repoducing on different special planet?

There is an animated sci/fi film i beleive created late 60's or 70's. Basically the plot is about these large alien type people who keep small human like people as pets, over time the pet humans get's back at the aliens by flying a rocket ship to a special planet where the aliens souls go to reproduce. Their souls are the silouettes of the aliens heads and the humans go to town. The end of the movie the human pets and aliens agree to mutally respect oneanother and they all lived happily ever after. What is the name of this thing?