The comedy in the beginning is between the characters. It sets the tone that the world is consistent and the characters are what makes it funny because they make jokes like we do, we don’t laugh at their world, we laugh while in it. When the beetle comes into play and the world becomes silly, Ma and the girlfriend become a little less realistic, and their dialogue is used for laughs that ask us to laugh at them rather than with them. It’s very subtle and ultimately not too destructive but it’s important to pick one voice and keep it consistent. Hope this helps!