Just in case you were running around like a chicken with it's head cut off today looking for an episode, there wasn't one! But what if there was?
It is now the year 2052, and you have stumbled upon the ruins of the lost Studio B building. While digging through the wreckage, you have uncovered a flash drive labeled "MLP_Season_3 - The Lost Episode". Perhaps it was controversial in some way and needed to be axed? A full on 22 minutes of Derpy delivering the mail maybe?
In the comments, toss a synopsis down for a season three lost episode!