This is reporter Thea Stilton in a keyhole sweater.
Thea Stilton is Geronimo Stilton's younger sister and the protagonist of her books. She is a special correspondent for the Rodent's Gazette (Geronimo's newspaper company). Unlike her brother, she absolutely adores travelling, going on adventures and meeting rodents from all around the world!
One of her favorite adventures begins at Mouseford Academy, the school she went to when she was just a young mouseling. When she came back to teach a journalism class (When she was a grown mouse) she met five special mouselings. They liked her so much that they decided to name their group the Thea Sisters after her! Thea was so touched by that, so she decided to write about the famouse adventures of those five mouselings.