Frozen's new short - Once Upon A Snowman - solves a small but annoying plot-hole from the original movie. The brief new chapter in the Frozen franchise, which released on Disney+, promised to answer the question of Olaf's origin, but in doing so, it filled in one niggling gap in Anna and Elsa's original tale.

Once Upon A Snowman is a funny but short look into Olaf the snowman's origin story, which may confuse some fans given that Frozen itself established how he came to existence. But cleverly, the new short - which runs just 6 minutes but has enough heart and laughs to delight Olaf fans - takes the same approach as The Lion King 1.5, showing what happened to Olaf from his point of creation to when he joined the action in Frozen. What could have been a frivolous cash-in on Olaf's popularity actually adds depth to the mythology of Frozen's world, building on the idea of water having memory in Frozen 2 and also of emotional bridges between characters being true magic.

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Crucially for anyone who was annoyed by one particular moment in Frozen, there's also an answer in among the new Frozen short's Easter Eggs to how Anna manages to trade with Oaken without having any currency. In the first movie, as fans have pointed out since its release, Kristoff turns away from Wandering Oaken's because of his inflated prices but Anna is able to buy not only her own supplies but the ones her future husband discards in disgust. Quite how she managed that was unclear, given that she was unlikely to carry money, but Once Upon A Snowman confirms that she traded the one valuable thing she did have.

When Olaf meets Oaken for the first time (they have a pre-existing relationship in the Frozen series thanks to another short, Olaf's Frozen Adventure), the hairy "bear man" as Olaf calls him helps the snowman choose possible options for his missing nose. And while that sequence brings about some of the best gags, the most notable narrative point for Frozen is in the background, where Anna's ornate ballgown is seen hanging for sale behind Oaken's counter. Clearly, the princess used her valuable dress as her currency and the price-tag of 55 suggests exactly how valuable it was, given that everything Kristoff attempted to buy in Frozen from Oaken should have cost just 10 (before the winter inflation).

Anna and Elsa's enforced isolation from the outside world - partly through their status and partly because of their parents' reluctance to allow Elsa's magical powers to be revealed and feared - meant that it would be unlikely that Anna would have experienced trading at all. The idea of her carrying her own currency simply doesn't fit what is established about her, so her somehow trading with Oaken for goods that Kristoff could not afford never rang entirely true. It's by no means a fatal story issue, but it was enough to warrant discussion online, and it's a testament to Frozen's commitment to storytelling that the new Frozen short, Once Upon A Snowman, adds that qualification.

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