William Scuttle, more commonly referred to as "Twit," is the fieldmouse cousin of Oswald Chitter. His mother is Gladwin Scuttle, whose sister is Arabel Chitter.

Twit is a best friend of Thomas Triton, and enjoys his rum. He is also known to be a simpleton- "no cheese upstairs". However, this is not a bad thing, as he sees good in everyone.

In The Crystal Prison, Twit accompanies Audrey Brown to the Fennywolde field to return to his family at last. After a frightening series of murders provokes the mice of Fenny to attempt to hang Audrey, Twit invokes the Gallows Law and proceeds to marry her. At first she believes the act was simply to save her neck; but at the end of the book, when Audrey and Arthur return to their home, it is shown that Twit truly loves her.

Twit's importance in the fate of the world cannot be underestimated. Together with Ogmund he will be instrumental in destroying one of the most ancient and powerful beings upon the earth.