Constable Haddock is a human member of the Ankh-Morpork City Watch. He appears to a be a capable copper who can turn his hand to many tasks - for instance, he is a trained coach-driver - and also moonlights, no doubt with Samuel Vimes's knowledge and consent, as a night-watchman at the Royal Bank of Ankh-Morpork. Here he is one of the horribly efficient security staff who Moist von Lipwig silently curses for not getting into bad habits and slacking off to have an all night poker game. In fact, he is so efficient as a Bank Watchman that he is the one who initially arrests Moist for breaking into the bank vault whilst equipped with a golem, a roll of lock-picks, and a blackjack. He appears in Thud!, Making Money, Unseen Academicals and briefly in I Shall Wear Midnight. He is affectionately known as "Kipper".
In I Shall Wear Midnight, Haddock is charged with tricky diplomacy, in that he has to persuade two witches to come quietly and help the Watch with their inquiries. In Unseen Academicals, he arrests Trevor Likely on suspicion of murder. In Snuff, he is on a diplomatic exchange to Quirm and has been promoted to Acting-Captain, with Vimes promising to promote him to sergeant thanks to his tenacious ability of writing down everything that people promise.