Igors appear in :- Carpe Jugulum, The Fifth Elephant, an Igorina in Monstrous Regiment, Thief of Time… and I'm sure I've missed some. Originating in Uberwald they are the official servants of any self respecting mad scientist. Considering disposal of unused human parts as waste, they are all gifted surgeons always ready to lend a hand, or a foot, or whatever is needed in case of accident- and are frequently self made men, not wishing to use any techniques on others before trying them out on themselves. Thus, your average Igor (they're all called Igor, to avoid confusion) will have a spare heart and possibly his grandfathers eyes (assuming the former was no longer using them), and though the lopsided, asymetrical look is in vogue, and visible seams are a must, they are still very popular with the ladies.
Thus, though parts of an Igor have once belonged to someone who is now dead, an Igor is not technically one of the undead.