Following the super success of Disney's 'Frozen', which has been declared as the highest earning animated movie ever, fans have now started speculating about the storyline of its sequel, 'Frozen 2'.

Since very little detail is known about the upcoming movie, fans are wondering whether the same voice actors will return for 'Frozen 2' when the movie will hit the theaters.

Meanwhile, a report by the IBTimes has stated that the sequel to 'Frozen' is likely to have a much darker theme compared to the original. In fact, several news websites dedicated to the film industry have been speculating that Disney may have a darker plot for 'Frozen 2'.

According to Latin Post, the plot of 'Frozen 2' may be based on the original Hans Christian Andersen story, 'The Snow Queen'. The website further says that Hans Christian Andersen's fairy tale may be the basis of 'Frozen 2'. Incidentally, this fairy tale does not have a very happy ending.

In 'The Snow Queen', the main protagonist Gerda has to choose between good and evil. Andersen's fairy tale is set in a magical land where an evil elf creates a magic mirror that only depicts the bad aspects in everything. Kai, Gerda's friend, discovers the mirror and turn out to be mean and cruel by repeatedly looking into the mirror.

Later, the queen of the land abducts Kai, who is forced to forget Gerda, who launches a search for her friend and eventually visits the palace of the Snow Queen. Greda locates Kai and kisses him with a view to break the spell cast by the Snow Queen.

In the original 'Frozen' movie, viewers see Princess Anna going on an adventure to discover as well as bring back her elder sister, Queen Elsa, who had fled owing to her magical icy powers. The classic movie was written and directed Chris Buck.

All said and done, Disney has yet to corroborate on the story of 'Frozen 2' and if main characters of the original 'Frozen' - Elsa, Anna, Olaf and Kristoff, will be returning for the sequel.