Aryanne, Ponyville's resident Nazi sympathizer, unicorn supremacist, and self-hating earth pony, gets asked to be the substitute teacher for Ms. Cheerilee's class when the latter pony falls ill one morning. During a lecture about the finer points of eugenics, Ayranne discovers that the ponies of Ponyville aren't quite as excited about the Final Solution as she is.
As with most of my stories, you have the Seattle's Angels skype group to thank for this one.