"I wish that Aunt Cathy was a centaur and that I was back in my own time" you said and with that you disappeared to go back to your time.
Aunt Cathy felt a tingling near the end of her spine. She noticed that her pants were beginning to bulge near her butt.She quickly pulled her pants off to relieve the pressure.She had a graceful black horse tail now.That's not all she noticed.Her belly began to bulge outward creating pressure between her shirt.She realized too late that her expanding belly would rip her shirt to shreds if she didn't pull it off.Before she could move, her belly ripped through the shirt, showing a big horse belly. Her whole body felt extremely itchy, it felt it was thousands of pin pricks poking her.It was only brown horse hair.She waited a few minutes and didn't feel any more changes.Satisfied,she sat up in her bed and rubbed her big horse belly.She idly rubbed the fur on it,when she felt a low rumble in her stomach."Wow, I'm starved."she thought.She put her hand to her face and felt that her face had formed a small muzzle.
When you went back to the point that you went back in time you saw Cathy as a centaur trotting around and you noticed that Sara came up to her and you looked in shock that she was also a Centaur.
Sara trotted up to you and said