|Relatives:||Grandchildren: Geronimo, Thea and Trap Stilton|
Great-grandchildren: Benjamin Stilton and Pandora Spring
William Shortpaws started his newspaper empire as a mouselet by selling newspapers before starting his own newspaper at home when he got older. After he retired and passed on the company to his grandson Geronimo, he took up golf as a hobby.
His favorite grandchild is clearly Thea as he gives her anything she wants. However, whenever he pays a visit to the Rodent's Gazette, he gives Geronimo a lot of grief and orders him around.
- His name was spelled Maximillan Mousemower for the first couple of books. This was eventually changed. The meaning of this is still unknown, however he is still called this on the Scholastic Geronimo Stilton website.
- He owns a cheese-colored camper which he uses it to travel anywhere.