"What if they were sisters"? Was the idea that no one remembers who said first, but was the one that changed the fortunes of ‘The Snow Queen’ story forever. Already the team had come up with adapting Andersen’s Gerta into a new character named Anna and now they just needed something to tie her and the Snow Queen together - making them siblings was the key the story needed to finally take off. It also helped that now on board was animator Peter del Vecho and ‘Wreck it Ralph’s' Jennifer Lee, who would eventually become the first female Disney director with 'Frozen'. Another turing point was the composition of the song ‘Let it Go’, which would go on to receive the Academy Award for best song. 'Avenue Q' songwriting duo Robert Lopez and Kristen Anderson-Lopez had been brought in to write for the film but their interpretation of Elsa was different than the villain the writers had first imagined. The pair saw her as a more complex vulnerable character, 'Let It Go' becam the theme which her character was based on. Elsa was then changed from and out and out villain and script began turning into the 'Frozen' we now know.

Of course once the writers had the story figured out the cast was then assembled with Kristen Bell, who had been best known as 'Veronica Mars', picked to play Anna and Broadway star Idina Menzel as Elsa the snow queen of Arendelle. Extensive research was then done on how to achieve the perfect snowy setting with the team travelling to Norway to soak up the scenery before drawing the magical looking Arendelle.

FrozenDisney's 'Frozen' went on to pick up two Oscars

Well all know how the story ended, ‘Frozen’ went on to not only break box office records, but also to win the Oscar for best animated picutre. It’s won praise for its script, characterisations, animation as well as the voice work of its cast, with principle characters of Anna and Elsa being held up as a new kind of Disney princess, one which we're all a lot more happy about. Maybe though the most amazing part of the 'Frozen' story is just how long it took to be realised, 70 years! That's a long time to be set on one story without it coming to fruition. Maybe the time just had to be right for 'Frozen' and luckily for Disney winter 2013 became the perfect time to thaw this classic story.

More: 'Frozen' Is The Biggest Animated Movie Of All Time: Step Aside 'Toy Story 3'

More: Listen To 'Let It Go' From 'Frozen'

Watch the Frozen trailer: