Star Trek II: The Wrath of Khan - Button That Uniform!
When Spock is dying within the glass confines of the ships nuclear power source room with Admiral Kirk (William Shatner) on the opposite side of the glass, in one scene speaking to Spock, Admiral Kirk's red Federation uniform jacket lapel is unbuttoned at the top. In the very next scene the uniform jacket is buttoned.
Khan remembers Chekov from the original series, but the character of Chekov did not appear on the series until the second season. The episode "Space Seed" which Khan originally appears was a first season episode. In the original screenplay of "The Wraith of Khan" there was a scene where Chekov is looking at a computer file which tells about the crews first encounter with Khan, but this does not explain how Khan recognizes him.