These guys got an extended License from Hasbro to release the shirts, for those wondering how this is official.
You can find the website for them below!
Pony Shirts 2
Thanks to M M For the heads up, and Operator on Ponychan for the find!
Description: With Luna's return, Celestia finds herself with more free time than she's had in a thousand years, perhaps even time enough to pursue a little romance. At the same time, Luna has to come to terms with a world that has become very different from the one she's used to, especially if she's going to help her sister.Never Too Old To Fall
Description: Spike wants to impress Rarity and gets Twilight's aid in order to make this happen. But the plan backfires, as a spell meant for Spike instead hits Rarity, turning Spike's Princess into a Prince.Prince Elusive and Sir Spike
Description: Berry Punch is a pony with many demons trying to be a good mother, and Colgate just wants to help.Bottled Up: Bite of Lime
Description: When Applejack comes down with the terrible Piebald Fever, it's up to Apple Bloom to travel to the faraway Valley of Eternal Torment in search of a cure. What unimaginable horrors await in the deep fog of the valley basin? Apple Bloom will soon discover that there is more at stake than simply her life!Apple Bloom and the Magical Rubious Crystal of Bellemare Sands