"Look, I'm really sorry I asked like that. I'm just really messed up now with all these changes!" You look back down at yuorself. Now that you think about it, being a kid again could be a lot of fun. But you'd like to at least get back past puberty. "How can I make it challenging? I mean, I don't know what you can do."
Red grins. "Describe what you want to look like, what you want to be able to do. Anything you want."
"Ummm." You think hard. "I'd like to be about 15 years old, with blonde hair and blue eyes, handsome, admired, really strong and muscular, able to run faster than any other kid my age. And I want to have a famous mother and father, and never have to worry about money or anything else. Oh, and I want to be able to speak at least three languages, plus English. And..." You flush slightly, but this is your only chance. "I'd like to be hung like a horse."
Red grins. "That's a tall order! You came up with a challenge, at least. Let's see." She reaches out and touches your nose. You feel a little shock, and suddenly start to get larger. Your baseball shirt changes into a loose T-shirt with 'Chiron Middle School' written across the front. But all of your other clothing disappears.
Muscles form and your hair starts to grow out, long, wavy, and blonde. You appear to be about 13 now, and though it is a little emberrasing to be naked, you can see you are getting pretty large between the legs. A rippling sensation starts at the top of your head and works down your body, and when it reaches your toes you are a powerfully built 15 year-old boy with shoulder-length blonde hair and man-sized equipment.
"Wow! This is great! Than..." Red cuts you off with a grin.
"Oh, I'm not done yet." She waves her hand and another spasm shoots from your waist down to your toes, which go numb. You lurch upwards, growing amazingly fast, and cry out as your legs throb and pull hard enough to make you stagger. But you find that you are steadier than ever when the feeling passes. Because you have four legs now! Horse legs to be exact, that go quite well with the powerful colt's body that starts at your waist.
You twist around and stare at yourself. "I'm a centaur!"
Red nods. "Everything you asked for, including being hung like a horse. Your parents are famous race horses, and you speak English, horse, mule, and donkey."
"But I'm a freak!"
Red nods. "Yeah, a scientific experiment. Lucky for you the lead scientist adopted you when they saw you had human intelligence and keep you as a companion and pet for thier children. When you grow up you'll be sent back to the stables, and you'll never have to worry about money or anything else."