Pua is Moana's loyal pet pig with puppy energy and an innocent puppy brain."
The idea of having a pig character came from the filmmakers' research trips to the South Pacific islands, where they learned that pigs and roosters regularly joined the voyages of wayfinders. Pua and Moana's rooster friend Heihei were created as the comic relief sidekicks as a result. In earlier versions of film, Pua had a much larger role and joined Moana's journey to find Maui and restore the heart of Te Fiti, alongside Heihei whom, in previous versions, had somewhat of a dislike towards both Pua and Moana.
A deleted scene also shows the origins of Moana and Pua's relationship. As a newborn part of the island's livestock, Pua had failing health as he did not eat. When Moana tried to feed him, her father Tui pulled her back, saying, "You can't force him to eat". To save the piglet, Moana takes Pua and baby feeds him, herself. She then names him and deems him her pet.
However, writer Jared Bush believed Moana's journey should be as difficult and uncomfortable as possible, and as such, Pua was scrapped from that portion of the movie. This stripped Moana of any confidantes and comforting friends, which added to the hardships of her mission, as planned. The decision was also made, partially, to keep Pua out of danger. Pua's removal from a majority of the movie received negative criticism from fans and critics, as many believed Pua was to play a larger role (as he was heavily featured in the movie's pre-release marketing) and were disappointed to find otherwise. Co-director John Musker admits to having mixed feelings about Pua's removal, even after the release of the film.
Despite being a pig, Pua typically acts like a puppy. He is perhaps Moana's biggest supporter. He cares a great deal for Moana's happiness, as well as her personal ambitions; specifically her yearning to sail the seas. In all cases, he happily joins Moana's side to assist her in any way he can. Though he is willing to face new challenges, however, Pua will not hesitate to back away should said challenge prove to be too intense or life-threatening.
Pua is first seen as part of Moana's childhood during "Where You Are". From there, he acts as Moana's sidekick and confidante throughout both her daily routines as the soon-to-be chief of Motonui and her downtime. Moana feels pulled to the sea despite her father's law that forbids anyone from leaving the island. Pua, however, supports Moana and feels saddened whenever she's forcibly distracted from her apparent calling. When the island falls under a curse that slowly destroys their food supply, Moana believes the only solution is to go beyond the island's barrier reef to find food elsewhere. Tui forbids this, prompting Moana and Pua to go out alone. The further out they go, the more dangerous the waters become. Soon enough, the boat is struck by a powerful wave that nearly drowns both Moana and Pua. They manage to make it to the shore, but the experience traumatizes Pua so much that the mere sight of Moana's oar causes him to run back to the village in fear. When Gramma Tala sees the damage, she playfully advises Moana to blame it on Pua.
Pua is not seen again until the very end of the film, where Moana returns home from her quest to save the island. As she embraces her parents, the villagers come to greet her, with Pua being the most excited to reunite with his friend. During the finale reprise of "We Know the Way", Pua is seen sailing with Moana and her family (with Heihei atop of his head) as they revive their island's voyaging roots.
An emoticon version of Pua appeared near the beginning and the end of the As Told by Emoji retelling of Moana.