The most important character who undergoes changes is of course Nora. Nora particularly changes from feeling that she is happy in marriage to realizing that her entire marriage has been a complete fraud. We see Nora profess to her friend Christine what she believes is her happiness in her marriage in the very first act. When Christine says that she has no children and that she is all alone in the world, Nora gushes about her "three lovely children" (I). She also effuses about Torvald's new position as manager of the bank, saying:
For the future we can live quite differently--we can do just as we like. I feel so relieved and so happy, Christine! (I).
All of Nora's boasts about her children and Torvald's new position shows us just how happy she thinks she is. However, that all changes by the end of the play. At the end of the play when Torvald demands of her, "Nora! Have you not been happy here?," she replies, "No, I have never been happy. I thought I was, but it has never really been so ... only merry" (III). The change in Nora's attitude about her position is due to her realization that her husband has never understood her, never loved her selflessly as she thought he had, and never really taken her seriously. Hence, Nora changes in the play from a naive wife who thinks she is happy into an adult woman who now understands that she has the right to be treated as an equal and "reasonable human being" (III).
A second character that changes in the play is Krogstad. Out of desperation to save his job, he blackmails Nora by exposing her secret forgery to her husband. But before Torvald has a chance to read the letter, Christine talks with Krogstad about their past together. She asks Krogstad to forgive her for leaving him for a man that was better off financially in order to care for her ill mother and two brothers. She also asks Krogstad to allow her to be his wife. Krogstad feels so relieved and rejuvenated that someone would still have enough faith in his character to want to marry him that he repents writing the letter to Torvald that exposes Nora and endangers both Torvald's and Nora's reputations. Krogstad is so repentant that he would have even waited for Torvald to return from the costume party in order to tell Torvald not to read the letter. However, Christine forbade it. Christine feels it is better for Nora's sake that her husband learns the truth.