It seemed like it was going to be a perfect morning for Twilight, until she realized she had woken up with Rarity and Rainbow Dash, tenderly cuddling next to her on the bed. Just what the hay happened last night? And why do they keep calling Twilight 'mistress'?

Mood Wings - Observations on Pegasus Body Language.

When Twilight Sparkle finds this book, she discovers an entirely new field of research. The secrets of pegasus wings lie before her, and she insists on making her own observations on the matter.

How?

Field research, of course.

Fluttershy gets more than she asked for when she visits the Library and hears moaning from behind the door. Concerned that Twilight may have developed a problem, Rarity and Rainbow Dash go and investigate.

Fluttershy and Twilight run afoul of some new breed of Poison Joke. It sends them into a nightmarish trip into a dark, terrible and beautiful land, where danger lurks around every turn, and beauty waits over every hill.