Percy's cat. Footnote comes aboard The Spotted Custard along with Percy, becoming the ship's resident cat.
Footnote is a tuxedo cat, mostly black with white markings, as if dressed for the theater. He has white stomach markings up to his throat, white spats, long white whiskers, and a white tail tip.
- Gail has admitted that she based Footnote on her own cat, Lilliput, also a tuxedo. Although Lilliput is female, smaller, and doesn't have a white tail tip.
- Footnote helps seal negotiations with the Drifters in Imprudence, because cats are seen as the living soul of the ship.
- "Upon hearing his name, said cat stood up from behind a pile of books and swayed over, emitting a chirrup of inquiry." (Prudence, Chapter Three)
- "He was an attractive animal, mostly black with white markings, as though smartly dressed for the theatre. Better dressed than Percy ever was, that's certain." (Prudence, Chapter Three)
- "Footnote appeared, stretched at them in his version of a bow and sniffed their shoes. They stood still, allowing him to do so until, gatekeeper-like, he magnanimously began leading them through the books, tail high." (Prudence, Chapter Seven)
- “She put her tea down and buried her face in Footnote’s fuzzy coat, which smelled faintly of cheese.” (Imprudence, Chapter Four)
- “Footnote made an appearance at that juncture, ambling up in a welcoming manner until he spotted Tasherit, at which point his tail bristled up like a bottlebrush and he hissed.” (Imprudence, Chapter Nine)
- “Footnote subsided into a loaf position, looking like an upended Christmas pudding with interested ears.” (Imprudence, Chapter Nine)