This story is very similar to a fairy tale because an outside force sweeps in and changes the character’s life.
In some ways, Pip’s story is a Cinderella story. Cinderella was abused and forced to stay out of normal life and society. Pip was also abused and secluded. Cinderella received supernatural intervention in the form of a Fairy Godmother. Pip also received intervention, although there was nothing supernatural about it. Consider it fate.
Cinderella’s Fairy Godmother transformed her into a princess worthy of marrying her prince. In a way, Magwitch did the same thing with Pip. He was impressed with Pip’s generosity to him when he was an escaped convict. He also wanted to prove that anyone could be a gentleman. Pip was whisked away to London to be trained for high society. Like Cinderella, this involved new clothes. I guess the clothes really do make the man!
Just as Cinderella’s fairy godmother prepared her to meet her prince, Pip’s fairy godfather prepared him for his princess. Pip assumed that he was being groomed to marry Estella. Of course, what really happened is that Estella had no interest in him, and Miss Havisham was not his benefactor.
Even Pip compares his and Estella’s story to a fairy tale.
She had adopted Estella, she had as good as adopted me, and it could not fail to be her intention to bring us together. She reserved it for me to restore the desolate house, admit the sunshine into the dark rooms, set the clocks a going and the cold hearths a blazing, tear down the cobwebs, destroy the vermin—in short, do all the shining deeds of the young Knight of romance, and marry the Princess. (Ch. 29)
In this fairy tale, there is no happy ending. Estella and Pip are unhappy, and will remain unhappy. Neither of them knows how to love in the normal sense. Pip is obsessed with Estella, and Estella is irrevocably broken. Pip was transformed by his fairy godfather, but his princess was not ready to marry him.
The importance of the fairy tale for this story is that Dickens is telling us that you can't transform yourself for the one you love. It is a rather pessimistic love story that Pip and Estella share. The people who are in love in the normal, simple way are much happier. Joe and Biddy, Herbert and Clara, and Wemmick and Miss Skiffins all live happily ever after, but Pip and Estella will be forever mourning the lives they could have had.