It's Luna's birthday, and the Mane Six decides that, hey, we have pets of our own but the princesses don't! I'm sure they'll like what Pinkie and Fluttershy picked out. Why them? Why not!
There are a lot of things this show has taught me. When I started watching, I never expected it to affect me as much as it has. But now that I'm here, I don't know what I'd do without you all!