Triton

King Triton is the widowed father of Ariel and her six older sisters and the sea king of Atlantica.

The Little Mermaid
In the original film, Triton is xenophobic toward humans and Ariel's fascination with humans casts a strain on their relationship. According to Triton, contact between the human world and the merworld is strictly forbidden.

Triton first appears at a concert in Atlantica, presented by the seahorse serving as the host. After Sebastian the crab, the distinguished royal court composer, and Triton's loyal servant is presented, Triton and Sebastian have a discussion about how they anticipate the concert due to Ariel, Triton's youngest daughter, is supposed to make her musical debut. But Ariel turns out to be absent, much to Triton's extreme fury.

After an initial argument with Ariel over her latest trip to the surface, Triton orders Sebastian to keep an eye on her. When Triton learns that Ariel saved the life of, and fallen in love with, a human being, he loses his temper and, determined to turn Ariel over to his views of humans, destroys her collection of human things, completely ignoring his daughter's pleas to stop. In the aftermath, Triton instantly horrified over his actions, leaves Ariel tearfully alone in her grotto in shame.

Later on, after Ariel swims away from home in search of the sea witch Ursula and becomes human, Triton orders a search for her to apologize for what he had done, unaware that she has accepted Ursula's deal and become a human. He asks Seahorse Herald if any sign of Ariel and Sebastian and he replies that they searched everywhere and no traces of them and Triton orders them to keep looking and no one sleeps until they return home safe and sound and he sadly did so. Triton is briefly seen suffering extreme remorse over what he had done, blaming himself for his daughter's disappearance.

When Sebastian, who had been watching over Ariel, arrives from the surface and tells the king about Ursula's scheme, Triton quickly goes out with Sebastian to find her. Ariel apologizes to her father, who attempts to destroy the contract between Ariel and Ursula, to no avail. Upon learning from Ursula that Ariel had signed an agreement with Ursula and that she may be willing to make an exchange for someone even better, Triton willingly takes his daughter's place, despite knowing the cost of his choice. Triton is temporarily transformed into a polyp, but after Ursula is destroyed, he is restored to his original form and regains both his crown and his trident, as well as his regal status.

By the end of the film, Triton has softened his attitude and realized that he had made a mistake by thinking humans were vicious and that he had been wrong in doing so. Upon noticing how much Ariel loves Prince Eric (who had destroyed Ursula and subsequently not only saved Triton's life, but also the entire kingdom of Atlantica) as much as she is loved by Triton, as well as considering Sebastian's statement "Children got to be free to lead their own lives", Triton transforms Ariel into a human once again, allowing Ariel to be with Eric. He is later seen at the wedding of Ariel and Eric, where he gives his daughter a heartwarming hug and accepts Eric as his son-in-law; when Eric bowed, smiling, Triton returned the smile as though thanking him for saving his life and the kingdom of Atlantica.

Trivia

 * He is the first Disney King that isn't a human.
 * It appears that Queen Athena's death had changed King Triton's life and the laws of Atlantica.
 * Banned Music from Atlantica (but was later brought back).
 * Forbidden to make contact with the surface world (later changes the law due to Ariel loving Eric).
 * Banished Ursula from Atlantica. (Not seen in Ariel's Beginning but in the TV series).