Log Horizon: do some Landers know that their world used to be just a game where they were NPCs?
Can't reply to some of the other comments but we can't forget that the translation system could be shielding the Landers from the abnormal phrasing like Game, NPCs, Real Life, Other World, etc.

Translations could be:
Game = before world fraction.
NPC = Landers.
Real Life = past Life.
Etc