The Hidden Library

"The cold never bothered me anyway."

In which Anna and Elsa find a very old book put away in the depths of a gigantic library they didn't even know they had in the castle, entitled Human Legends of the Guardians. Anna believes all the legends they read about, but Elsa refuses to believe them all because, according to her, they're just legends.

When Jack Frost appears to her one night, it's obvious she lied.