Even if you haven’t read the TwiBrush trilogy — and let’s face it, most people haven’t — you may have seen this passage therefrom in Vent #794, in which the earth pony-to-be addresses the unicorn he loves:
“Twi, honey, there’s only one thing wrong with you: you can’t stand the idea that there’s one thing wrong with you. You seem to be able to put up with my flaws just fine. Can’t you cut yourself a little slack now and then? I don’t want to come home some day and find you’ve put a Starvation Spell on yourself because you farted in the bathtub the night before. But you make me worry about things like that, and it scares me.”
It did not occur to me at the time that she might be harvesting the stuff for semi-medicinal purposes.