MLP: Diapered Disciple (private with Perdente)
 

Lina is pacing around the front of the castle, awaiting Twilight’s arrival. She told Twilight that she is looking for an understudy and has invited Twilight to take on the task.

Twilight wasn't awfully anxious about seeing Luna. She seemed generally more relaxed than Celestia, in certain ways. However, Twilight's 'not awfully anxious'ness involved carrying practically an entire library in her saddlebags! At the top of Luna's tower, she knocked at the door.

Luna did not hesitate to open the door. “Good afternoon, Twilight. Pleased to see that you were able to show up today. Why don’t thou come inside?”

Twilight entered as she was asked.

"Now then." Luna opened another door in her bedroom. "Through here, please."

Twilight walked where she was directed, confused about her surroundings, and a bit intimidated.

"I can see you are confused, and rightly so." Luna said as she used her magic and a magic inhibitor ring appeared around Twilight's horn and some metal cuffs appeared around Twilight's wings. "I was looking for a little foal to take care of. Just imagine how fun it would be feeding you, dressing you up and bathing you."

"I'm... I'm afraid I don't, HEY!" Twilight shouted, feeling her magic suddenly dim, and her wings suddenly fold, "Wh-What did you just do!?"

"That should just keep you from using your magic. I need you as helpless as a baby. Now, let's get you on that changing table. You are going to be diapered.

"Wh-What are you talking about!?" Twilight said, as she was magically lifted up and carried.