The Thea Sisters are a group of young mouselets who currently attend Mouseford Academy. The group consists of Nicky, Violet, Colette, Paulina, and Pamela. They got their group's name from Thea Stilton, who teaches them in their journalism courses and more, and serves as their mentor. The Thea Stilton books are based on the five girls and their adventures all around the world (and out), where they have mysteries to solve in each one.
The Thea Sisters have gone on many adventures since Thea met them as a teacher in their journalism course. Traveling all over the world and out, they have gone to Australia, China, Peru, France, Japan, the USA (New York, Alaska, Hawaii, and California (Hollywood)), the moon, Scotland, Egypt, India, Turkey, Italy (Milan and Venice), Spain, Kenya, Tunisia, the Netherlands, Ireland, Ecuador, Greece, Russia, the Bahamas, Madagascar, Iceland, Norway, and Canada. Usually their adventures lead them on missions and quests, which are mostly unexpected. They always find the culprit in the end and always make new friends on their adventures.
- Nicky - She is an Australian mouselet who loves being outside. She is the athlete and one of two jokesters in the group, and her love of the outdoors most likely stems from her claustrophobia, or fear of tight spaces.
- Colette - Coming from France, Colette is very particular about her appearance, but is energetic and full of great ideas. Like almost anyone who has an eye for fashion, Colette has a tendency to be fashionably late.
- Violet - Hailing from the land of China, Violet is a shy mouselet who dreams of being a great violinist. She is the intellectual of the group and is always open to learning something new. While she is intelligent and very artistic and detail-oriented, Violet is a bit sensitive and can't survive without sleep.
- Paulina - From the land of the Incas (aka Peru), Paulina is the computer genius of the group. She is kind and loves meeting new people and going to new places. However, she can be shy at times and is kinda clumsy.
- Pamela - If you're looking for a mechanic, look no further than Pam. Her family is from Tanzania, and she is the pacifist, mechanic, second jokester, and ball of enthusiasm in the group. She loves pizza, and she can practically fix anything with just a screwdriver. One tiny flaw about her, however, is that she's impulsive.