Milli has red hair held in ponytails or pigtails and rosy cheeks. Without her helmet, her ponytails are bigger and fuller. With her helmet, her ponytails are flat and ribbon-like. She mostly wears a shirt over a dress and a helmet, tight stockings and Converse-like Mary-Janes. The outfit's default colour is pink and the dress and helmet have a default pattern of pink flowers. The outfit changes colour and pattern See Milli's Many Patterns. She has definite age to be six years old, according to the Team Umizoomi website.
Milli-Measure: Milli's pigtails, but she prefers "ponytails", become a ruler, scale, Etc. She can also use it to add measurements to specific things, which was revealed in one of their promos.
Pattern Power: In episodes up to "The Big Boat Race", Pattern Power is, basically, applying a pattern onto an item. In episodes starting with "The Dinosaur Museum Mishap", Milli changes her dress into a pattern mostly to add something missing to the pattern by peeling the picture of the item off with that picture fading then more colour added, to fix a pattern or to follow a pattern to get through obstacles. Examples of her dress patterns are on Milli's Many Patterns.
Ponytails: Milli's hair extends to her liking. See more on Milli-Measure.
Karate: Milli knows how to do karate. She has powerful chop, kick, even her ponytails. She mostly uses her skills to get past pattern and remove measurements or to divide something into fractions.
Milli is really sweet, cute, and generous, but don't let her cute looks and sweetness fool you. Despite being six years old, she is also fearless, strong, and would do anything to help and save her friends. That's why she's the leader of Team Umizoomi. She's also the strongest member of the team.
Even though she really loves and cares for her brother Geo, as seen in Milli Saves The Day where she comes to his and Bot's rescue, Milli sometimes doesn't have faith in Geo with his ideas at first.
Revealed in The Kitty Rescue, her favourite animals are bunnies. Milli has a female pet bunny named Whispers. In Umi Toy Store, Milli revealed to have some experience in playing the toy piano.
Milli is known as the animal-lover on the team. She just can't stand the sight of baby animals so much, that she can jump for joy. Her love for animals make her a great rider of animals. From horses, to dinosaur, to even dragons, Milli is not afraid to ride any single type of animals, and she always asked before getting on animals.
It is known is that Milli was born before Geo. It is not known how her ponytails can grow and shrink and how her dress has the ability to change patterns. It is not revealed to how she and Geo met Bot. Her parents and other relatives are not revealed as well. However, only relative that was revealed was her brother, Geo.