Ya burnt!

Matters of doctrinal dispute, too, give rise to the occasional sly squib. The early Irish Church had its differences with Rome, for example on the thorny question of the dating of Easter, which led to a “great dispute” and a resulting Irish hostility towards St Peter, the founder of the Roman Church… Thus on the recto of folio 180, a line of text referring to Peter’s denial of Christ incorporates the figure of a hare, an animal known for its timidity.

From John Banville’s article about the Book of Kells in the Financial Times.  Above is Lindisfarne, from Wikipedia.