Although his origins are unknown, it can be presumed that Igor was a creation of Dr. Appalling's. Although little is known about him and his physical appearance is intimidating, Igor (which "rhymes with Seymour!") seems to be very mild-mannered.
Igor was accidentally neutralized by Dr. Appalling and reduced to chattering teeth, but he was soon miraculously resurrected, and an invention that Junior made resulted in blooms of flowers sticking up from his head to compensate for his baldness.