|Family||Geo (brother), Bot (Guardian), UmiCar|
|Abilities||Pattern Power, Measuring|
|First Appearance||The Big Boat Race (chronologically), The Kite Festival (airing order)|
|Voiced By||Sofia Fox (Season 1), Madeline Rose Yen (Season 2-present)|
Milli is the leader of Team Umizoomi and sister to Geo. She is the primary protagonist.
Milli has red hair held in ponytails(or pigtails) and rosy cheeks. Without her helmet, her ponytails are bigger and fuller. With the helmet, her ponytails are flat and ribbon-like. She mostly wears a dress and a helmet, tight stockings and Mary-Jane shoes. The outfit's default color is pink and the dress and helmet have a pattern of pink flowers. The outfit changes color and pattern (See Pattern Power) Sometimes when someone or Milli mentions her dress, she curtsies for fun. She is confirmed to be six years old, according to the website.
In Movie Madness!, she has only one ponytail in some of the movies.
- 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 somthing missing to the pattern by peeling the picture of the item off with that picture fading then more color 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. 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.
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 animals, and she always asked before getting on animals.
It is known is that Milli was born before Geo. It is unknown how her ponytails can grow and shrink and how her dress has the ability to change patterns.
- As of Milli Saves The Day, Milli is the only member to go on a mission alone.
- "Milli" happens to a prefix meaning "By the thousandth" or just "thousand". It may also be based of the word "chameleon" since she can change colors kind of like a real chameleon.
- Milli is the only main protagonist with a confirmed age (She is six years old).
- For some reason in some Team Umizoomi products, Milli's clothing has a more reddish tone.
- In one episode, it is revealed that without her ponytails, she has very long red hair.
- Out of all the members of Team Umizoomi, so far, Milli is the only member to not be in trouble.
- According to polls, Milli is the favorite member of Team Umizoomi.
- "That tricky Shape Bandit!" (from Team Umizoomi VS. The Shape Bandit)
- "Uh, guys?" (in numerous episodes)