This movie has a few easter eggs and interesting trivia.
On one of Oaken's shelves is a plush Mickey Mouse
Both Idina and Kristen had auditioned for the role of Rapunzel in Tangled.
A live reindeer was brought into the animating studio for animators to study its movements and mannerisms for the reindeer character, Sven. Co-director Jennifer Lee said it was the best moment during production for her.
Kristen Bell stated that with this film, she has fulfilled a lifelong dream of voicing an animated character ever since she saw The Little Mermaid(1989) and Aladdin (1992) as a kid. When she was around that same age, she recorded a voice box where she sang a couple of songs from The Little Mermaid, including "Part of Your World". Her Little Mermaid vocal tracks were part of the reason why she got the part of Anna, as director Jennifer Lee said to her that if she hadn't recorded her own vocal tracks from Mermaid, it would've been very difficult to the find the right one to play Anna.
The characters of Anna, Hans, and Kristof are all named after Hans Christian Andersen: Prince Hans as in Hans, (Krist)of as in (Christ)ian, and (An)na as in (An)dersen