 FAIR: Although some object that Chekov wasnt part of the Enterprise  crew in the episode "Space Seed" and therefore Khan could not have  remembered his "face", in fact it is possible (according to Star  Trek apologists) that Chekov *was* a crewmember at that time, merely  not a member of the bridge crew. The earlier encounter between him  and Khan might have taken place between "Space Seed" scenes.