Maxwell Smart encounters Agent 13's evil doppelganger.
Division of KAOS which scours the globe searching for exact physical duplicates of CONTROL personnel with the intention of training them to replace the originals.
Only one member of the League of Impostors has been positively identified by name - Yohan, a duplicate of Maxwell Smart - but it is known that League members have also impersonated Agents 13 and 38, as well as the Chief of CONTROL himself [Episode #63: "The Spy Who Met Himself"].
Although it is not specifically stated, it is possible that Sonja, a 99 lookalike, was also a member of the League [Episode #133: "And Only Two Ninety-Nine"].
Another conjectural member is the agent who impersonates Spanish Secret Service agent Jose Vargas, distinguishable only when observed signing his name with his right hand - the real Vargas is left-handed [Episode #98: "Temporarily Out of CONTROL"].