During a shopping trip in 101 AG, Penga had a large tantrum and inadvertently moved Toph's bracelet ever so slightly with her latent bending abilities. The earthbending master thus recruited her for her academy, assuming she had the potential to become a metalbender. However, progress was slow, as she had yet to move a single coin by the time that Sokka visited the academy.
When the Water Tribe warrior visited the school, Penga developed an immediate crush on him, claiming him to be her boyfriend. As Toph caught her pupils leaving the academy, they explained to her that the school had been taken over by firebender students of the Master Kunyo's Firebending Dojo, and Penga complained that they had not even let her pack her shoes. Toph negotiated with Master Kunyo for ownership of the building, and it was mutually decided that a competition would be held between the students to decide which group would be able to use it.
Having managed to buy the students three extra days to practice, Toph and Sokka tried many different methods to teach Penga and her two peers to bend metal. During one of these attempts, Sokka decided that since the students had originally moved Toph's bracelet unintentionally while in extremely emotional states, all they needed to do was recreate that state. To achieve this, Sokka scared Penga with a big metal monster who had supposedly stolen and eaten all her shoes. However, instead of being able to metalbend, she broke down in complete shock.
The evening prior to the battle, Penga and the other students prepared to entirely quit the academy when they overheard Toph admitting to Sokka that she had been expecting them to be something they were not. Inspired by the fact that someone expected her to be more than "a spoiled brat", she and the other students discovered the key to metalbending and were able to bend metal coins, thus defeating the rival firebending school. Afterward, Penga declared that she was over Sokka and that Ho Tun was the one for her. She and her peers subsequently returned to training.
When Toph and Sokka briefly departed the Metalbending Academy with Suki, Penga and the other students were told to stay behind and continue practicing their metalbending. Penga tried to convince her teacher to let her go along by showing Toph her "spinny helmet trick", but Toph dismissed her firmly and expressed her lack of confidence in her student's abilities. Later, however, Penga and her peers came to fight in the battle for Yu Dao. Their timely appearance saved Toph and Suki, and spurred Toph to compliment Penga on her metalbending skills.
After Toph departed from the academy to see her friends, Penga, Ho Tun, and The Dark One became its temporary instructors. During a lesson, Sokka arrived, telling them they needed to come with him. Penga clung to his arm, asking if he was trying to reignite their romance as she was over him, but was told by Ho Tun to stop because the situation looked serious.
The students arrived to the town where the Earthen Fire Refinery was located, where they met up with Aang, who explained the situation to them: Toph and several others were trapped underground and he could not dig them out due to the iron ore deposits in the ground; he thus needed their metalbending to do so. Katara added that Toph stated it to be like spider ants stomping beneath their feet, which Penga explained to them was an exercise where, while standing blindfolded in a sand pit, they needed to bend giant metal plates back and forth over their heads, plates even bigger than Ho Tun. Upon Ho Tun asking if they were ready, Penga noted that there was a lot of iron beneath them and began bending on her fellow student's call. They soon revealed a giant iron mask before continuing, telling the other metalbenders to stay focused on the mission. Soon enough, she could feel the space where the group was and, with one last heave and Aang's help, they freed them. Toph complemented them on their job, but after she collapsed into her father's arms, Penga grew worried, though Lao assured them that she was just exhausted and would be fine. When Ho Tun commented she looked small and almost fragile, Penga warned him that such comments could get him pummeled by their sifu. Learning that Lao was Toph's father, Penga was surprised and, when asked as such by Ho Tun, believed that Toph popping out of a rock would make sense.
The students continued to stand near their instructor as she rested. However, when they learned that Aang was about to destroy the Earthen Fire Refinery and Toph awoke, she called on them to help her stop him. They raised an earthen wall to stop his attacks. They were blown off the wall by Aang's air rings but landed softly on their feet before returning to the battle. Toph called on them to metalbend, but their attacks were dodged. Penga soon noticed the giant spirit, General Old Iron, approaching them, asking if that was the same one Aang mentioned earlier as to why he had to destroy the refinery. With an intense battle between the spirit and Avatar, Toph again called on the three, but this time to help Aang. This confused the younger metalbender as they were just trying to fight him off. Nonetheless, Toph continued by saying they needed to use their bending to peel off the armor, just like the forest bowing to the east wind exercise, something Penga hated almost as much as the spider ants stomping beneath feet technique. They were able to do so and thus give Aang an open shot to the spirit's chest, but Old Iron soon noticed that the four metalbenders were destroying his armor, thus turning his attention them. Toph told them to run while she held him off, though Penga did not want to abandon her. They soon watched as Aang delivered a severe blow to Old Iron and the vanquished spirit gave a speech about how humans were more powerful than him before walking away.
Three months later, Penga participated in the parade for the new Spirits' Friendship Festival, playing an Air Nomad flute as the procession made its way down the town's main street.
Penga had a curious and clingy nature. She had a close relationship with her parents, fearing they would be harmed in the riots during the Harmony Restoration Movement. She was passionate about shoes, often requesting that they be purchased for her. She also seemed to be rather spoiled, demonstrated when she was walked around by servants and wanting shoes even though she had already bought tons of things and used all the shopping money her parents provided her.
She had an odd infatuation with Sokka, and decided that he would be her new boyfriend, and became very clingy toward him, despite the fact that Sokka did not talk to her much or even give off hints that he liked her. However, after she found out Ho Tun could metalbend, she declared him her new boyfriend, and was done with Sokka. Later, she developed a metalbending trick she called the "spinny helmet trick". Penga, Ho Tun, and The Dark One used this technique to turn the Fire Nation soldiers' helmets so they could not see, and helped Toph when she was in trouble.
Penga was an earthbender enrolled by her parents in Toph's new metalbending academy, although Toph believed she needed substantial practice in order to learn metalbending. She, like the other metalbending students, was chosen for the school because she caused Toph's bracelet to move when she grew very emotional. She eventually became the second metalbending pupil.