In which Discord and Fluttershy go to the store and buy two cakes. In the process, Discord ends up having an interesting conversation with Pinkie.

Somewhat spoilery for Make New Friends but Keep Discord, but not enough to ruin the episode if you do decide to read it. However, if you're really squeamish about spoilers, I suggest you stay away.
Takes place sometime before the Gala, but after Tirek.