Pirate Barker Oh was an enthusiastic and somewhat goofy lieutenant to the pirate captain. Although a non-bender, he was very skilled with a sword and small, hand-held explosives. He did not know the meaning of the word "curios" and referred to himself as a "high-risk trader" rather than a pirate. Oh's personality was unlike most pirates, as he saved his aggressive side for fighting, but was usually confident when talking to people, especially when he thought he could make a sale or a good deal.
Around 99 ASC, the pirate ship of which Oh was a member docked at the seedy merchants pier, and Oh attempted to entice passersby to enter the ship and peruse the many curiosities aboard. As Team Avatar walked by, he addressed them as world travelers, based on their clothing, and managed to persuade them to visit the boutique on the ship. While the three friends looked around, Oh remained in a corner and watched the ship's captain haggle with Aang over a waterbending scroll. He amicably confirmed Sokka's accusation of being a pirate, by retorting that they rather think about themselves as "high-risk traders".
Shortly after they group had left the ship, Oh ran out on deck and called after them, as the pirates had discovered that Katara had stolen the scroll. He pursued them with his fellow pirates though the small town in an attempt to retrieve the stolen item, and managed to corner them, threatening to kill them. However, his plans were foiled by Aang, who airbent at him to provide cover for their escape. As the friends flew over, Oh received a kick in the face from Sokka, and could do nothing more than witness their escape.
He reported back to his captain about their failed mission. At that moment, Zuko and Iroh were on the ship as well, and the young Fire NationPrince struck a deal with them: capture Aang in exchange for the waterbending scroll. However, the deal went sour when the pirates learned that they had the Avatar in custody. As Zuko and his firebenders attacked, Oh nimbly jumped out of the way of the blast and charged them, using his superior agility to avoid incoming blasts, while throwing three small marble-like smoke bombs at the Fire Nation troops. He drew his swords and jumped in the smoke cloud, ready to engage his foes.
In the commotion of the ensuing battle, Team Avatar managed to escape with the pirate's ship, thus prompting Oh and the others to commandeer Zuko's boat to pursue their own. Oh was among the boarding party and engaged Sokka in battle to regain control over the ship. However, he found himself wedged between the legs of the Water Tribe warrior, though his companion managed to overpower the young man and throw him against the sail under the approving eyes of Oh. His triumph was short-lived, however, as Aang swiftly blasted him off with a powerful air sphere. He managed to hang on to the ship and confronted Aang again. Losing focus as the monk did not retaliate but blew his bison whistle instead, Oh was overpowered and thrown overboard by Sokka who had sneaked up behind him. As he floated in the water, he was hit on the head with Iroh's White Lotus Pai Sho tile, which Zuko had angrily thrown into the lagoon.
The experience with Zuko and his soldiers did not cause Oh to harbor any hard feelings toward dealing with Fire Nation people, as he was willing to strike another deal with them. Together with the other pirates, he made a deal with Zhao to kill Zuko in exchange for a chest of gold, which he claimed to be "tasty" after he had checked its authenticity by biting on it. He and several others sneaked onto Zuko's ship to position barrels of blasting jelly. After all the barrels were placed correctly, Oh lit the line of powder and high-tailed off the ship before it detonated. However, Oh inadvertently saved Zuko's life by making noise while opening a door, prompting the prince to go look for the cause of the noise.