What is the common theme of "The Secret Life of Walter Mitty" and "The Necklace" besides gender roles and/or marriage?
If I were answering this question I would definitely want to focus on the element of daydreaming in both of these stories and how they dominate the central characters. "The Secret Life of Walter Mitty" is of course a story that is entirely about a man who day dreams to escape his boring, monotonous existence and his overpowering wife. The dreams he has place him in situations of adventure and allow him to be the man that he would never be in reality, as he is always the hero of the piece and the one that everyone looks up to. Dreams for Walter Mitty help him to endure his painful insignificant existence as he copes with his nagging wife:
"Not so fast! You're driving too fast!" said Mrs. Mitty. "What are you driving so fast for?"
However, in "The Necklace," dreams are another escape for Madame Loisel, but ultimately one that causes her and her husband great pain and suffering. She is a woman who is addicted to daydreaming a better life for herself, and imagining wealth and luxury that she is not able to possess:
She would dream of silent chambers, draped with Oriental tapestries and lighted by tall bronze floor lamps, and of two handsome butlers in knee breeches, who, drowsy from the heavy warmth cast by the central stove, dozed in large overstuffed armchairs.
Here, however, dreams function as an expression of Madame Loisel's inability to accept what she has in life and be grateful for it, in comparison to Walter Mitty, who dreams to survive. Madame Loisel is duly punished for her daydreaming, whereas Mitty is free, as far as we know, to continue dreaming and escaping.