Tom-Tom was Mai's younger brother and the beloved son of Ukano, the former governor of New Ozai, and his wife, Michi. As a two-year-old, Tom-Tom did not understand the conflict his family was involved in. Both curious and mischievous, he innocently got himself in and out of all kinds of trouble.
Tom-Tom wandered away from his parents, who were distracted by the plague of "pentapox". He was playing with a stuffed animal in a room when he spotted Momo eating berries on a table. Tom-Tom spotted the lemur's dangling tail and pulled it, forcing Momo off the table and onto the floor with Tom-Tom. As Momo tried to escape, Tom-Tom followed him and they ended up together with the escaping citizens of Omashu. Out of curiosity, the infant followed the citizens and the two eventually wound up at the rebel campsite. Katara took special delight in Tom-Tom, cuddling him and commenting on how cute he was, although Yung said he would just be another soldier when he grew up, calling the baby a killer. AvatarAang returned after failing to locate KingBumi and, not long after, a messenger hawk appeared bearing a message from Ukano, who was under the impression that the earthbenders had kidnapped Tom-Tom, using the disease as their cover and offered to trade Bumi for Tom-Tom.
Azula arrived in New Ozai to speak with Mai, and decided that they, alongside Ty Lee, would handle the exchange so that there would be no more hindrances. When the three girls showed up at the rendezvous point, they brought King Bumi, but they decided to go back on the deal after considering that trading a baby for a powerful earthbender king would be a foolish decision.
Later, Aang went to the governor's house and anonymously returned Tom-Tom, much to the joy of his parents. In the course of the next two years, he also learned to speak.
After the end of the Hundred Year War, Tom-Tom's father took him to the New Ozai Society in an attempt to raise him to be more loyal to the former Fire Lord. At the meeting, he was very happy to see Mai again after so long. However, after his sister refused their father's offer to join the society, she took Tom-Tom and had him stay with her at their Aunt Mura's.