Parodied in Friendship is Witchcraft. At the beginning of 'Cute from the Hip', Cheerilee gives a paranoid and seemingly irrelevant lesson about robots and the dangers they pose to society. It's played off as some sort of Freudian justification for why her husband has been distant lately. But then at the end of the episode we're introduced to Sweetie Belle, who is quite obviously a robot. No one notices or remembers the lesson.
In the universe of Greek Ninja, the students of Ariadnio learn to fight and thus, not get killed during its invasions, from simply attending it (since it's a martial arts school). Subverted in Sasha's case, who even points out herself that she learnt everything from Yamauchi-sensei.
Helluva Boss: In "The Harvest Moon Festival", Moxxie rattles off his knowledge of angelic weaponry in a failed attempt to impress his in-laws. Later on, he ends up discovering an angelic weapon in Striker's room; he quickly recognizes it as one of the few weapons around that can kill demon royalty, leading to him discovering that Striker is planning on killing Stolas.
In the Whateley Universe story "Ayla and the Tests", Phase misses several days of school and gets a big lecture in the lab section for Powers Theory class from Dr. Yablonski on Warper powers and warp displacement fields of 'giants' (Warpers who use their power to apparently grow to huge size). In a Lampshade Hanging, Phase even refers to him as Mister Exposition. Guess what Phase faces when they go to Boston? A forty-foot giant who's a warper.
In "Ayla and the Birthday Brawl", Ayla shows (s)he knows too much about taking out mutants with powers, and she talks all about it on the way back from martial arts class. What she says about fighting Package Deal Psychics saves Lancer's life in the big final fight.
Of course, Whateley Academy is a Super Hero School, so it's more than usually justified.
