King Neptune is a Triton and he is the King of the Seas of Andros.
He is the father of the twin brothers Nereus and Tritannus as well as the uncle of Aisha, and as such he could be the brother or brother-in-law of either King Teredor or Queen Niobe. Queen Ligea is his wife with whom he has three children, Nereus, Tritannus, and Tressa. It is revealed in the last episode of Season Five that Teredor is his brother, therefore making him Aisha's paternal uncle.
Neptune has a slight tan, and white hair. He has a long white beard and wears a golden crown. He has beady black eyes and violet eyebrows. He wears a sash like think around his chest and neck, which has a golden and blue circle on it. He is a half triton, with a fish-like hood. The sides of his body are blue and fish like. Below, he wears a golden belt which holds his sword and has a large blue tail.
After Tritannus mutated him, he looks identical to Tritannus' other mutants in which his build becomes skinny, has an ill colored skin tone with many wrinkles to his face and transparent flaps beneath his arms.
Neptune is very stern and strict, he honors duty above all and does not tolerate inappropriate behavior. However, he is shown to care and love his family, even Tritannus as he is seen deeply sadden by the fact that he must imprison his own son for his crimes.
In Season 5, he decided to name Nereus as his heir but a jealous Tritannus disrupted the ceremony and was sent to prison.
After Tritannus's escape, he disowned Tritannus and set out to hunt him down. He was later turned into a mutant along with Tressa when Tritannus invaded the palace. He made some minor appearances after the ceremony.
In the final episode, he and Ligea were relinquished from Tritannus' spell thanks to Bloom and Nereus. He then goes to the surface with his wife, Tritannus, Daphne, Bloom, Aisha and Nereus, and he was greeted by everyone as they rejoiced for their safe return. After Nereus gives Tritannus one more chance to redeem himself, Tritannus voiced out in bitterness that he did not succeed in annihilating them, leading Neptune to punish his son by sending him to Oblivion.
He then attends Andros' celebration party with his whole family.
- Neptune is the brother of Teredor, although it has not been explained in the show how a Triton and a Human can be biological brothers.
- According to Roman mythology, Neptune is the God of the Sea. The Greek equivalent of Neptune, Poseidon, is married to Amphitrite, a Nereid nymph, one of the fifty daughters of the God Nereus, and with her had a son: the marine God Triton, who is half-man half-fish. Amphitrite also has a sister named Galatea.
- Neptune is also the eighth planet of the Solar System and was named after the god Neptune.
- In the Original/Italian dub, his name is Nettuno.