Anyone who goes looking through fairy tales, reading broadly across thrice ten kingdoms or more, will find many things. Talking cats, and foxes, and wolves. Dragons no larger than a human. Mother-in-law problems. Boulders at crossroads carved with warnings for the traveler about every direction forward. Kings who live across the street and heckle each other every morning.
And plot holes. Oh, so many plot holes.
What happened to the maid who was imprisoned with Maid Maleen in the tower for seven years after the two of them escaped the tower and found a job in another country, and she vanished from the tale without a mention? How on earth did the prince free Iron Hans from his curse? Why did the fox tell the gardener's youngest son to cut his head off only at the end of the story, when that was what was needed to turn him back to a human? Did the stepmother who turned her six stepsons into swans succeed in claiming the kingdom for her own son? What happened to the bride who was coming to marry the king when Catherine's Fortune arranged for the king to marry her instead?
Then, sticking to the Pop Top 20 doesn't exactly spare you. Why doesn't Cinderella's glass slipper change back like the rest of her finery? What happens when the king decides he wants the miller's daughter to spin more straw into gold? (Though he, too, vanishes from the story, before his child is born.) Did no one ever mention to the princess that the castle had been an ogre's, not the Marquis's? How do Hansel and Gretel and their father live on the gold and silver from the witch, if the problem is famine and no food to be bought?
Sometimes -- occasionally -- reading broadly provides an escape route, too. Oral tradition tends to pare things down, sometimes past sense, but it also tends to spread and to vary. Consequently, you can bring together tales to form a complete story.
I once decided to retell Child Ballad 53, Young Beichan, which is a recognizable fairy tale.1 During this ballad, Beichan forgets something rather memorable, but in the Scandinavian variants of this ballad, and the prose variants all over Europe, the hero forgets because he has been bewitched. Francis Child himself thought the motif might have been lost in this one, and I put it in -- or back in, as the case may be.
This, however, is rare. Most plot holes extend over the vast stretches of variants.
Then, given the brevity of fairy tales, even turning them into short stories requires adding, expanding, and developing characters, motives, background, and plot twists, and novels require still more. Fixing plot holes is one way to do this. Indeed, if you go for a Pop Top 20 tale, it may help with making this take on the tale be new and different.
For instance, when I was young, I read Andrew Lang's fairy books from Blue to Lilac, and thus when I read Sleeping Beauty, I read Charles Perrault's variant. Since pop culture, including Disney, opted for the Grimm Brothers' variant instead, most people do not know that Perrault did not end with the prince waking the princess up. No, the prince and princess married, and he hid her from his parents, because his mother was part ogre. They had two children, a daughter and a son. When his father died, he thought that he, as king, could protect them, but he had to go to war, and his mother tried to eat both the children and Sleeping Beauty herself. (Did I mention that fairy tales have a lot of mother-in-law problems?)
You may notice that I didn't mention what the fairy godmothers did at the christenings of the two children, or the christenings at all. This is because Perrault also entirely omitted them, and thus makes explicit the question that does hang about in the back of Sleeping Beauty: what happened the next time there was a christening of a princess, or a prince?
I poked at that idea one day. Hmm, I didn't want to wait the century out, but I could make the new baby her sister -- no, her cousin, because the idea took shape, and that would be better. Then I was off writing The Other Princess, about Sleeping Beauty's cousin, growing up overshadowed by her beautiful, tragic, cursed cousin. After all, given that all the fairies had been invited, the cousin had gotten only good, if mysterious, things at the christening.
Keep an eye out for those plot holes. You'll never know what will pop out of them.
If you wish to see the results of my wrestling, the Young Beichan short story is Over the Sea To Me, available at Amazon and many other fine venues:
https://www.amazon.com/Over-Sea-Me-Mary-Catelli-ebook/dp/B00ROPS6PA
and also The Other Princess novella
https://www.amazon.com/Other-Princess-Mary-Catelli-ebook/dp/B0B8XXS4CF
Ballads are merely stories told in songs. As a consequence, they range all over. Kinmont Willie is a historically accurate if slightly embellished account of the rescue of William Armstrong of Kinmont at one end, and at the other end, well, there are ballads like Young Beichan.
Two words: suspend disbelief.
And I gag while saying them.
By the way, hubby and I watch a British TV murder mystery series where some of the actions is sooooo contrived as to be totally implausible. Yet the show is very popular and still in production. We just set aside such things and enjoy the detectives catch the killer(s). Sigh.