He turned his head and smiled wanly as a girl in a black dress moved through the dark circle toward him, slipped her arm through his.
Her dress was too small; the dull material smashed her full breasts wide and flat, strained across her hips. Someone else must have picked out the dress, someone who hadn't noticed the girl had become womanly.
The girl leaned against her father, mutely accepting people's hands on her, a multitude of hands pressing the girl's arms, her shoulders and back. She turned stiffly to be kissed, whispered at.

As a little girl, she had been weak and sickly, suffering from an exceptionally poor constitution. Over the course of the next few weeks, Albert taught her various exercises to alter her metabolism.
After a time, the two of them finally went their separate ways, and Allison all but forgot about Albert.
It wasn't until years after parting from Albert that Allison discovered the odd side affect of her altered metabolism. Her body stopped growing when she was about eight years old. From that point on, the only way she could attain a body reflecting her true age was by using a technique to temporarily force herself to grow up in seconds.
Remaining stuck most of the time in an eight-year-old body had also had an unusual effect on her mental state. Despite her present age of twenty-four, Allison often behaved in a frivolous, child-like manner--especially while in her child age, though occasionally also as an adult.
On the other hand, she often displayed unusual wisdom and maturity, both appropriate to her adult form, but seeming odd coming from an eight-year-old.

At that very moment, Allison was in her child-form, as usual dressed in fashionable clothing (currently Gap Kids) which obviously fit her perfectly, but would be damaged and destroyed unpredictably if she chose to go forward to her curvaceous adult body.
(Nearly all of Allison's wardrobe that looked decent on a little girl of eight would be destroyed by the rising body of a girl growing through puberty, let alone on the body of a beauty of twenty-four. It was a difficulty the woman had to bear, though she admitted she was flattered by the looks she could draw as she grew into an adult.)
Allison was skipping down an uncrowded street, taking an occasional lick from a double-dipped triple fudge ice-cream cone (with sprinkles), and humming the ditty the ice-cream truck had been playing.

TO: Mike Topp - FR: Sparro
Subject: My Hand Is Now Too Small
Dream 7: I am playing a game of football with friends. At the same time, I am growing younger. Late in the game, I try to throw the football, but cannot. My hand is now too small.
Inimitably, Sparrow

  "EEEEEEEEEKKK!!!" Clarisa shrieked, leaping from her seat and darting out of the dining room like a speeding lightning bolt.
  "Could you do that again?"

  "But Daddy, I don't understa--"
Kathreen resisted the instinct to cringe in terror and begin to cry. Instead she stood tall and looked her father in the face.
  "Fine!" she lashed back. In an instant she grew almost a foot taller, her hair grew longer and wavier, her eyes became larger, her nose and ears changed and her face became more oval with age. And her growing body inevitably exposed its nakedness to her father as it passed the limits her clothes could hope to cover.
She stormed out of the study, leaving the door wide open behind her.

The ageshifter mother was amused to see the soft bulges in her girl-child's rising shirt were swelling as fast as the immeasurably hard shaft extending in her boy-child's pants. Litter-mates tended to ageshift at the same speed.
She felt her own nipples erect in sympathy and angrily sharpened her focus.
There was a loud crack and she felt the air move as her boy-child's penis broke through his pants and slammed against his hardening stomach.
As litter-mates, nothing would happen between them, but she would watch them closely.
The head of his penis was rising faster than the rest of his growing body, as both her children's clothes tore. All male ageshifters had enormous penises. He already knew he could only have sex with a Normal in his boy-form. If he lost control of his age-state she would be dead in seconds.

In college, I took a public speaking class with a girl whose nipples would get rock hard, like, glass-cutting hard, when it was her turn to stand in front of the group. It wasn't like she was wearing a thin shirt with no bra -- she was wearing normal clothes. When she wasn't presenting you couldn't see anything. But when she got up there, these things were just unstoppable. The juggernaut of nipples.
We were supposed to write feedback about the presentation. It was anonymous, so I figured... OK, it's a little embarrassing for her, but maybe she doesn't know? So I included it in my evaluation. I tried to be subtle... "You may want to dress warmer." After class I asked my friend and... yeah, he wrote about her nips too.
And so did everyone else I asked.
The next time she went up there, she kept her coat on, zipped up all the way - (Matt)

Anime with Female AR?
There's a brief scene in Brigadoon:
https://www.youtube.com/watch?v=rvl2A9NC-K0
And in Magical Warfare:
http://www.dailymotion.com/video/x1fmspw_magical-warfare-age-regression_tv
In MAR, character Loco gets younger everytime she uses her powers. She looks about 10 or 12 by the time the series starts, and eventually reverts to a baby in episode 92.
There's a brief omake at the end of episode 25 of Mirai Nikki (Future Diary, if you prefer its English name), where Yuno is accidentally turned into a baby:
https://www.youtube.com/watch?v=l0GDOrRMNTY
- (Azerty47)