Fairytale land has a rule, and that is that things happen in threes. Cinderella goes to the ball twice before the prince gets wise and smears pitch on the steps on the third night. Jack goes up the beanstalk three times. There were three little pigs. Rumplestiltskin gave the queen three guesses as to his name, and I believe Goldilocks ran into a trio of bears.
Of course there are counter examples: Snow White and the Seven Dwarves, Twelve Dancing Princesses, but three is the rule. Remember that in Snow White, the Queen tries to kill Snow White three times and the Twelve Dancing Princesses leave their chamber for three nights.
Why is this? Is there something magical or particularly fairy-like about the number three? I have a few theories…
Easy as 1, 2, 3: As these stories were first told orally and without written reference, three event stories were easiest to remember and retell: First, Next, Last. Copper, Silver, Gold. Straw, Wood, Brick. Hot, Cold, Just Right. This way, the teller doesn’t have to worry about the form, but can focus on improvising the juicy details and building dramatic tension (slowly, slowly, she turned the doorknob… creeeeeeaaaaak).
Two’s company, Three’s a pattern: Three establishes a rhythm and predictability to the story. Children can be assured that the two evil princes will fail when they try to pull the sword from the stone, but that the lowly orphan will succeed. The giant can be fooled twice, but the third time, he’ll catch on. The familiarity of a scenario being replayed is soothing to the child because it is easy to follow and predict.
Filler and Fluff: When your child calls out, “Tell me a story!” and you haven’t got anything on hand, who is ready to keep track of a Harry Potteresque alternate universe with a huge cast of characters and relationships? No one. So you start with a Princess and wing it. You throw in a few details that will titter (“and the Princess had a dog named Fuzzball” hey, that’s your dog’s name, too!). And you try to think of a way to make it last longer than 30 seconds. Um… Um… Traveling to the Sea was good, but now what? RULE OF THREE to the rescue! Do it over! Variations on a theme. Travel to the Mountains. Travel to the Woods. Put everything together (the Water, the Stone, the Wood) and presto: bestest, most magical castle EVAR!