Princess Celestia asked Twilight to do a census of her new home. Through this process she discovers certain anomalies that she finds strange as a unicorn. There seems to be something missing when it comes to the pegasi, and after much prodding, prying, some spying and begging, she finally gets them to open up. What she discovers is not only shocking (to her, at least), but revealing on pegasi subculture.

Will what she learns change the way she looks at her friends? Will her friendship with them be ruined?

Nah.