Cake Twins, Pound and Pumpkin, are now 15 years old and, along with Pinkie Pie, who is now 30 years old, still live at Sugarcube Corner. One day, the twins find a photo album of their old foal pictures. Halfway through, the twins start to miss their foalhood. So they decide to become teen foals. But the twins need a "foalsitter"

And who should be the one to do it? How about the mare that always used to do it?