Like his grandson, Triton, Neptune has golden armbands and a blue tail, but he is never seen wearing a golden crown.
Neptune appears in "Calliope Dreams" during a flashback to Triton's childhood. When Triton was young, Neptune would play the sea calliope nightly at bedtime. Triton would stay warm by the light of an electric eel and would listen to the calliope play until he fell asleep. Afterward, Neptune would carry his grandson to bed and tuck him in.
One day, when Neptune and Triton went to the room the calliope was in, they found the calliope completely destroyed. Unbeknownst to either of them, the ancient Seaclops was the one responsible, as the creature found the calliope's music disturbing.