Katie sighed as she viewed the shop she was essentially a prisoner in, her options were limited and she knew what she had to do. "Your not leaving me many choices here Merlin," she said. "I guess becoming your apprentice is my best option if I want to retain a part of myself."
Merlin smiled broadly and rubbed his hands together enthusiastically. "Excellent choice Katie," he said. "Trust me you won't regret this. Now, you have a choice, I can revive you as you would have been when you were sixteen, or I can transform you into my familiar and you may become my apprentice that way."
"What is a familiar?" Katie asked.
"It is a magical creature, uniquely bound to the wizard who summons or creates it. To anyone coming in the shop, it would seem that you were in costume or appearing as a normal human depending on the magic you wanted, but in reality you'd be something else."
So I would be an animal?" Katie pouted.
"Yes, but you would have a human or humanoid form as well." Merlin said. "This way you wouldn't have to grow up so quickly. People would think you were my daughter. It is your choice though."
Katie pondered as Merlin opened a book. There, on the page, were hundreds upon hundreds of mundane and fantastical animals. All she had to do was choose them, or his other offer.