This article focuses on Fiona Frizzle, the new teacher.
For the original Ms.Frizzle, see Valerie Frizzle.
As my big sister always says, Bus, do your stuff
—Fiona to Valerie

Fiona Felicity Frizzle (voiced by Kate McKinnon) is the very beautiful younger sister of Valerie Frizzle and John Frizzle. Upon her arrival, the entire class greets her as "Ms. Frizzle!" except for Arnold, who tells her "You're not Ms. Frizzle!" to which she replies "Oh, but I am, Arnold." At first, Fiona seems to be more concerned about the Safety of the ecosystem and not as concerned about the Dangers and Perils that befall her and the class while they're on their field trips. Fiona is only 7 minutes younger than Valerie as they are twins. Compared to Valerie, she has a more youthful physical appearance, similar to that of an average 25 – 35-year-old, while Valerie's is more of an appearance of a middle-aged person. While her outfits do reflect the theme of the day, they are not nearly as flamboyant as her sister's clothes. She typically wears a long-sleeved purple shirt, red ballet flats, and a necklace/skirt that showcases the theme of the day. Conversely, she might spend the entire episode in special gear like an astronaut suit, or a snow suit. Her theme colors are blue and purple. In the episode, the Magnetic Mambo, she is shown to be a talented dancer.


In addition to her beauty, Fiona is very intelligent and clever, very unique and compromising. She always has something planned out to teach the kids a fun way and very much cares for the bus. She enjoys rhyming and wincing like any other Frizzle.


Fiona has long red hair and green eyes. Her main outfit consists of a royal blue long sleeve shirt, a light blue skirt with patterns that change depending on the subject of the episode, and red ballet flats.