Yep. What Neil Armstrong meant to say was, “That’s one small step for a man, one giant leap for mankind.” But that isn’t quite what he said.
The radio transmissions from the Apollo 11 lunar module were of somewhat poor quality. If you listen to a tape of the transmissions, however, there can be a little doubt as to what Armstrong did say. After setting foot on the moon, Armstrong pauses a second or two and says, “That’s one small step for man, one giant leap for mankind.”
The omitted “a” is a small mistake but a particularly unfortunate one. “Man” without a preceding article means not one man but man in general, mankind. So Armstrong said, in effect, that’s one small step for mankind and one giant leap for mankind. He managed to create a local contradiction in the first eleven words spoken while standing on another planet.