In the episode "Luna Eclipsed" (S02E04) the ponies celebrate their own version of Halloween where the children have to "sacrifice" part of their candy to Night Mare Moon. It is stated throughout the episode that it is one of the most important nights in pony culture (as far as Equestria is concerned).
But in season 1, nopony had a clue who Night Mare Moon was, and nopony recognized her but Twilight.
Also, there is a huge lifelike statue of Night Mare Moon near Ponyville where the ponies make their candy sacrifice.
Given that Nightmare Night should be part of the calendar for at least a few centuries, it is too far fetched to assume that nopony in that assembly did not recognize her.
Was that event retconned in season two, or is there any other explanation to the presumed ignorance of the crowd in season one?