Igor is a capuchin monkey, considered the most intelligent New World monkeys in existence and often used in laboratories. He is the property of Dr. Boris Balinkoff, possibly named after his former manservant. Igor follows him back to the island with mind-control rings backed by a main control device to control the castaways. Igor soon watches from afar as Balinkoff takes Gilligan under his control and the Skipper and Ginger in turn. After Gilligan gets his ring back, Igor takes his turn playing with the machine and getting Gilligan to act like a monkey. Convinced his rings will work on anyone, Balinkoff has Igor distribute the rest of the rings, getting them to rehearse an attack on Fort Knox, but his remote control gets smashed and he has to cancel his scheme.
- Igor is not to be confused with Igor the Manservant or Igor the Cosmonaut.
- The monkey playing Igor is possibly the same monkey that reappears in Bang! Bang! Bang!.