Harmony is Hacker's five-year-old niece. She seems to be an average, sweet child who brings out the good in her "Unky Hacker". Hacker holds her in high regard and is much more willing to listen to her than to Buzz and Delete, even when they point out the same things. She is voiced by Lilly Bartlam.
Harmony's parents are unknown, as Dr. Marbles is not shown to have created any siblings for Hacker.
Harmony bears some resemblance to Hacker, with green skin, a pointed nose, and black hair, which appears slightly lighter than Hacker's wig. Unlike Hacker, she has a round face. She wears two purple hair bows in the shape of Hacker's bow tie, a lavender T-shirt, and purple overalls.