Sounds like Fall Weather Friends.
And I think we can enjoy some letters going the other way too. No guessing games from me, though.
Dear Twilight Sparkle, my most faithful student,
I've arrived in Fillydelphia and wouldn't you know it, this infestation is the same as the one Ponyville had. I- Oh please stop eating the paper. I'm trying to write a lett
Dear Twilight Sparkle, my student,
Why couldn't you have told me about the parasprites while I was visiting you? At the least you cou- Hey! HEY! Sto
Dear Twilight Sparkle,
These things sure are resilient, aren't they? I really wish you could have told me about- Oh not again! Will you CUT THAT O
Hey,
Why the HELL didn't you tell me about these monsters? Do you think this is some kind of joke? And that little mare with the band equipment? It's been long enough she should have been here by now! Or did you just go back to that stupid fucking library of yours to laugh at your mentor? When I get back to Canterlot I swear I'm going to- Oh that is IT! You think you can jerk ME around like that, you little pests? Watch this! I hope you like the sun, because you're about to see it REALLY CLOSE UP!