Kai and Gerda are both featured very briefly in the film. At the beginning, they are seen as members of the few servants who remain within the castle by orders of the King and Queen of Arendelle when the castle is locked away from the rest of the kingdom. Kai can be seen aiding the couple prior to their ill-fated sea voyage. When the King and Queen perish in a storm, Kai and another servant are seen veiling the royal portrait.
When the castle gates finally open for Elsa's coronation, Kai introduces the Duke of Weselton to the royal siblings at the coronation's ball, but accidentally mispronounces his name, leading him to be harshly corrected by the Duke.
After Elsa returns to Arendelle and lifts the winter curse, Kai is made aware of Hans' fate by a French dignitary. Kai then informs the Duke that Arendelle will be cutting ties with Weselton permanently, made official by Elsa herself. Much to the Duke's dismay, Kai pronounces his kingdom as "Weaseltown" on purpose to annoy him.
Kai and Gerda are last seen in the film skating on Elsa's newly created ice rink.
Gerda appears in the book A New Reindeer Friend, agreeing to Anna and Elsa's plan to have a ball.
- Kai: "Queen Elsa of Arendelle! Princess Anna of Arendelle!"
- Kai: "Your Majesty. The Duke of Weaseltown."
- Gerda: "Anna! You had us worried sick."
- Kai: "My Lady." (Kristoff: Get her warm. And find Prince Hans, immediately.) "We will. Thank you."
- Gerda: "Oh, you poor girl, you're freezing. Oh, let's get you inside now and get you warm."
- Kai: "He's in here. Prince Hans!"
- Gerda: "We'll give you two some privacy."
- Kai: "Arendelle thanks you, milord."
- Kai: "Oh. I have a message from the queen. 'Arendelle will henceforth and forever no longer do business of any sort with Weaseltown.'"
- Kai and Gerda are both named after the protagonists of the original "Snow Queen" tale by Hans Christian Andersen, by which Frozen was inspired. In the original story, Kai was the imperiled best friend (brother in some interpretations) of Gerda, a brave heroine determined to rescue him from The Snow Queen.
- In Once Upon a Time, Gerda is the Queen's name, so it has been speculated that Kai is the name of the King, but this is unconfirmed.
- Gerda was originally going to have an extra quote in the film as shown in the final shooting draft, when she thanks Hans while he is in charge of Arendelle.