Oona

Oona is a character in the Sofia the First special Sofia the First: The Floating Palace. She is a mermaid who befriends Sofia, when she gets kidnapped by a sea monster, Sofia with the help of Cora go save her.

Background
Oona first meets Sofia when she comes to the surface to take a closer look at the Floating Palace. She accidently gets caught in a net until Sofia untangles her. The two of them soon become friends and after Sofia's amulet gives her the power to become a mermaid they dive into the ocean together.

Oona takes Sofia to her hideaway where they meet Sven and her older sister Cora who treats like a "mer-baby."

Trivia

 * Oona becomes the first and only other princess to learn and witness the magic of Sofia's Amulet.
 * Like Sofia and her amulet, Oona wears a magical comb which gives her the power to control waves making her the second princess in the series to possess a magical object.
 * Even though she has the magical comb, Oona isn't shown yet how to use its power. In fact she never uses it. This makes her more of a vessel than a wielder so far in the franchise which is further supported by the fact that the comb has a spell on it that prevents anyone from physically taking it from her.
 * Like Ariel, Oona can not only talk to sea creatures but also to land animals.
 * Like Ariel's Secret Grotto, Oona has a secret hideaway that is a sunken shipwreck, where she keeps all her treasures.
 * Oona shares the same name with the mermaid character from Nick Jr's Bubble Guppies.