At band practice and after explaining to the others about what cutie marks are and where they appear, Pinkie and Rainbow get a crazy idea and manage convince the others into going to a tattoo parlor to get tattooed versions of their pony counterpart’s cutie marks, right on both of their butt cheeks no less. And upon getting them, the girls discover a certain thrill that they had never felt before...

All seven of them are 18 btw.