Master Pakku is the waterbending master from the Northern Water Tribe who agreed to teach Aang and Katara along with his other students. Although he led the defense forces against Zhao's in the Siege of the North, he did not appear to be answerable to Tribal PrincessYue, much like his animated counterpart with Arnook. In the novelization, he was not one of the ruling elders sitting with Princess Yue on the royal throne, he was sitting quietly in the corner when Katara addressed to the royal court. When Katara asked if there is a waterbending master who can teach Aang, "all eyes immediately turned in the corner" suggesting that the decision was for Pakku to make, not Yue. As such, the Northern waterbenders (led by Pakku) fit the modern-day definition of a militia and elites of their society.
In the movie, when Team Avatar arrived at the Northern Water Tribe, Pakku immediately devised a defensive strategy against an impending Fire Nation attack. After briefing the strategy, he insisted that a guard be assigned to Yue at all times - Sokka volunteered for the assignment, which he did not object. Pakku taught waterbending to Aang and Katara along with his other students. He fought bravely against multiple Fire Nation soldiers in the courtyard during the Siege of the North. He was last seen bowing to Aang with the rest of the tribe.
Although Pakku was not named in the theatrical cut of the movie, his name was listed in the end credits as Master Pakku. Also, in the deleted scene "Water Teaches Us Emotion", Katara addressed him as "Master Pakku".
Pakku did not seem sexist in the movie, nor did he showed any recognition to Katara's necklace and its significance to her grandmother, like in the series. He immediately accepted both Aang and Katara without any issues in his waterbending class.
His concept of waterbending is: "To master water you must release your emotions wherever they may lead you. Water teaches us acceptance. Let your emotions flow like water." This is different compared to the original "push-and-pull" concept in the series. This theory comes came into conflict with Aang's tapping into his immense waterbending ability, until the Dragon Spirit advised him to also let go of his guilt over the overwhelming loss of his people and the heavy burdens he has been forced to bear, to unleash the power of water.
Pakku and the Northern waterbenders were not part of the Northern Water Tribe government and military. As elites and a private militia, their role in leading the Northern Water Tribe forces during the Siege of the North was similar to the Jedi Knights (of Star Wars) in leading the Republic forces during the Clone Wars.
Despite his white hair, he appears to have a brown mustache, and black eyebrows.