Sunset Shimmer and Starlight Glimmer are on their way to meet Sunset's friends in the Canterlot Mall when Starlight is hit with a familiar urge in an unfamiliar place. Fortunately Sunset's been there before...
Takes place during the third Equestria Girls - Magical Movie Night special, "Mirror Magic", but no spoilers.
TOILET USE WITHIN. Don't read on if you have a problem with that.