Agent Z is a fictitious character in a series of four comical children’s books written by British author Mark Haddon, better known for his 2003 novel The Curious Incident of the Dog in the Night-time. In the first published versions of the books Haddon also did the artwork for the covers and a number of illustrations inside (the cover pictures were changed for later editions). The Agent Z series is set in the present day in an unnamed British city. In 1996 Agent Z and the Penguin from Mars was adapted for television by the BBC.