The human ears on the ducks, the musical change when the daddy is singing, and the way he sings, the uncertain fate of the tadpoles, the dolly being dizzy in the head because the daddy says so, the fact that the daughter is a doll,… so many reasons: https://m.youtube.com/watch?v=PWMAYFNIAco
I wonder if they did a lot of drawings in dirt to get practice.