Agnarr ruled at the throne alongside his wife, Queen Iduna. During his reign, he was ably assisted by his servant, Kai. Agnarr's oldest daughter, Elsa, was born with the power to control ice and snow. Neither Agnarr, Iduna, or Anna possess magical abilities of their own, singling Elsa out from the crowd. Despite this, Agnarr has some knowledge of magic, as he was aware of the existence of healing trolls.
Judging by how he presents himself, Agnarr is learned, kind, powerful, and diligent. His personality is further explored in the novel A Frozen Heart, where it is revealed that Agnarr had the tendency to spoil his daughters, and had a difficult time legitimately punishing them when they misbehave. Whenever he loses his temper, Iduna was able to calm his nerves.
Agnarr's primary concern was his daughters. He was willing to make large sacrifices to ensure their safety. He did not fear Elsa's magic, only the hardships that may befall her should her abilities remain untamed. In fact, he appeared optimistic that she would one day learn to control her abilities, noting that the drastic isolation was only temporary.
The king's name was not in the film's credits, but is written in the Runic alphabet on his memorial stone markers. According to that, his name is Agðar (English: Agdar/Agnarr). However, this was not confirmed by the filmmakers.
- The King's Name: Agðar can be anglicized as Agdar. Agðar is a male form of Agða, a short form of Agatha, meaning 'good, honorable.' Agdar is a popular name in Norway. The name Agdar means 'brave warrior' in Norse and from Greek agathos, meaning 'good'.
- Due to the Runic alphabet, the king's name can also be read as Akðar or Akthar. Some believe it could be the name Akhtar, which means 'star' and 'good luck'. The latter name is found in India, Pakistan, and Bangladesh as well as Iran as a surname thus making it unlikely to be the given name of a Nordic King.
In the middle of the night, Elsa and Anna sneak into the Grand Hall to create a winter wonderland for their enjoyment. During their playtime, Elsa accidentally strikes Anna in the head with her powers, rendering the latter unconscious. Agnarr and Iduna quickly arrive onto the scene upon hearing the distressed calls of Elsa. Agnarr uncovers a map leading to a valley inhabited by magical, healing trolls. The king of the trolls, Grand Pabbie, cleanses Anna's body of all magic, including memories of magic, meaning Anna will have no memory of Elsa's powers. Pabbie then informs the royal family that, while Elsa's magic is beautiful, she must learn to control it and not let fear consume her; should she do otherwise, horrible events may occur. Agnarr nevertheless assures his wife that Anna will be protected, and Elsa will eventually learn to control her abilities.
Having taken Pabbie's saying of "fear will be your enemy" literally, Agnarr limits Elsa's contact with others by separating her and Anna and reducing the castle staff. He also locked the castle gates, limiting contact between the castle and the outside world. As the years pass, and Elsa grows, Agnarr works with Elsa to better control her abilities, teaching her to conceal her powers by concealing her emotions. To further help, Agnarr instructs Elsa to wear gloves, and coins the mantra, "Conceal it, don't feel it, don't let it show", which Elsa would carry into adulthood.
One day, Agnarr and Iduna are to set off on a two-week sea voyage. During a storm, they are drowned at sea by monstrous waves. Anna and all the people of Arendelle mourn their deaths (a portrait of the couple is draped over with a black sheet of fabric), but Elsa does not attend. Due to the untimely tragedy, Elsa's training was left incomplete, her powers still mostly out of her control.
Agnarr appears later in the film; in a painting of his own coronation seen hanging in the library of the castle when Elsa was trying to control her powers, and again when Prince Hans betrays Anna in order to take over the kingdom. He and Iduna are indirectly mentioned when Kristoff asks Anna during their argument over Anna getting engaged to Hans after just meeting him, "Didn't your parents ever warn you about strangers?" to which Anna replies (rather uncomfortably), "Yes, they did." while slowly moving away from him.
Agnarr and Iduna briefly appear in Elsa's flashback during the reprise of "Ring in the Season". When Anna asks Elsa if their family has any holiday traditions, the only instance that Elsa could recall was the annual ringing of the Yule bell, although Anna pointed out that the Yule bell ceremony was more for the kingdom, rather than something personal to their family.
The King appears in live-action form in the first episode of the fourth season, portrayed by Oliver Rice. When Elsa exhibits powerful and dangerous ice powers, he and wife travel to the nearby land of Misthaven to find a wizard to get rid of her magic. While returning home, the ship is caught in a maelstrom.
- Many fans have noted that Agnarr bears a striking resemblance to Walt Disney in his younger years.
- It should also be noted that like the King, Walt had two daughters, Diane Marie Disney and Sharon Mae Disney.
- In the Frozen book illustrations, Agnarr has dark hair, but in the movie, he has light hair.
- In Frozen: Live at the Hyperion, Agnarr briefly returns as a spirit watching over his reunited daughters, during the finale.