Uma is Oobi's little sister. Both her stature and attention span are shorter than Oobi's. She is full of energy and occasionally makes mistakes due to thinking and acting too quickly. Uma does not always put the feelings of others into consideration, and depends on Oobi and Grampu for help when she does not understand something or needs to calm down. Uma loves to dance and her favorite animal is the chicken.
A running gag is Uma's inability to pronounce larger words that she is unfamiliar with, such as "asparagus" and "majorette". Whenever she encounters such a word, Oobi helps her figure out how to say it. After she learns a new word, she tends to say it constantly in conversation afterwards.
According to promotional statements for the show's first season, Uma is three years old at the beginning of the series. She celebrates her birthday in "Uma's Birthday!" and turns four years old. As of "Uma Preschool!", she attends a preschool class along with her best friend Moppie.
Uma has fair skin and five fingers. Her eyes are blue and her fingernails are a light pink color. Four fingers act as Uma's upper lip while her thumb acts as her lower lip. She wears a blue and purple barrette in full-length episodes of the show. The size and appearance of her barrette is changed slightly for the second season, and it retains this new look for the rest of the series.