Well, it's incorrectly regarded as a goof. The Incas discovered chocolate, not the Aztecs (I might be wrong, actually). But this kind of stupidity in an "educational" film (think about the six colonies on the moon that were built in 1960) is what makes it so funny. Oh, and the moon was clearly held up with strings (Actually that's the Secret War Of Lisa Simpson)
And someone was about to say something about something, and I could tell that FOX was being stupid.