Beginning around The Fifth Elephant, Igors have been a constant presence in Terry Pratchett's Discworld books. There, "Igor" is both the name of the individual and his occupation.
Any given Igor is a member of an extended family of Igors, all named Igor. They hail from the pseudo-Germanic country of Uberwald, where there's never a shortage of mad scientists in need of an obediant assistant to fetch the brains, mix the chemicals, and answer the door the instant it's knocked upon.
Igors all share a passionate interest in self-improvement, inheriting and adding body parts whenever they think they'll come in handy. When an Igor says he has his father's hands, he means it literally. The result is an ambulatory patchwork of stitches, mismatched facial features, and extra digits, but Igors don't mind. They're a practical bunch, and it adds to their recognizability.
Most Igors have a lisp and a hunchback, although some of the younger ones have begun rebelling against these traditions. Not all of them serve as scientific assistants, either; one works for the Ankh-Morpork Night Watch as a surgeon and forensic expert.
Igors are widely available throughout the Disc thanks to a special temp agency set up from Uberwald, "Igors R Us". Any Igor can be delivered (by overnight express, if necessary) to any city on demand, ready to serve any scientist or craftsman in need.