Why does the speaker use the phrase "good gracious" instead of "good heavens" all in sudden?
This is a bit of a humorous point. The movie is about the world of animals, so presumably they would not have an understanding of, or belief, in religion. The concept of "heaven" applies only to humans, so he corrects himself after saying "good heavens" to "good gracious," as they are exclamations of surprise that allude to God. Ex: Good heavens! You scared me. Ex: Good gracious, that car almost hit us.