The Cheshire Cat in Jasper Fforde's Thursday Next series Renamed "the Unitary Authority of Warrington Cat" due to changing boundaries, this cat is the overseer in the Great Library, a library within the book world, which contains every book ever written. The Unitary Authority cat turns out to be quite helpful to Thursday in her quest.
Thursday Next series by Jasper Fforde: The Eyre Affair (2001), Lost in a Good Book (2002), The Well of Lost Plots (2003), Something Rotten (2004), First Among Sequels (2008), One of our Thursdays is Missing (2011), The Woman Who Died a Lot (2012)
Welcome to a surreal version of Great Britain, where time travel is routine, cloning is a reality (dodos are the resurrected pet of choice), and literature is taken very, very seriously. All this is business as usual for Thursday Next, renowned Special Operative in literary detection, until someone begins kidnapping characters from works of literature. When Jane Eyre is plucked from the pages of Brontë's novel, Thursday must enter the novel herself to avert an act of literary homicide.