A young man in the audience stands up. "I'm willing to give the kid a few years - how old does he want to be?"
"25! I want to be a grownup, where nobody will question me or tell me what to do!"
Madame Illusia smiles. "Well, 12 years older. Tell me, sir, are you willing to help this young man? I can offer a two for one special."
"Two for one?" The man shrugs. "Yeah, that's good. He gets twelve years older and I get six years younger. I liked being 24. Sure, I'll do it!" He walks to the stage and stands next to the boy.
Madame Illusia grins, as if she just heard a good joke. "Well, now. Audience, you heard him accept my offer. As I said, two for one. But perhaps not the way our older friend here expects."
Both man and boy are suddenly surrounded by a bright glow, and they start to change. The boy gets a little taller, 14 now, the man loses some weight and appears younger. The boy is 15 now, and the man is definitely younger looking. His clothes seem a little loose, and a slight pot belly he had is now gone. As the boy stretches out through a growth spurt to 16, then 17, the young man is starting to look like he is already in his early 20s.
The audience starts to chuckle, for some of them realize what is happening. The boy matures quickly now, 18, 19, 20. At the same time, the man is dropping age even faster. For a moment, the two of them look like fellow college students, then the boy's face begins to darken as his beard gets heavier, and the former adult loses height and weight as he regresses into high school.
The former boy is staring at his muscular body, and rubs a hand over the hair that spreads down his arms. The glow is fading now, and he is a trim and handsome 25 year-old version of the 13 year-old boy.
"Hey!" A scrawney little 6 year-old boy stares at himself in sudden horror. His clothing has changed to fit both his size and age, with a bright orange jumper replacing his slacks and sports shirt. The opposite has occurred with the now grown boy.
Madame Illusia goes to the stunned child. "I never said how the two-for-one worked. You got two years younger for every year he got older."
"But I can't stay like this!" The boy is crying. "I have a wife and a child! I have a job, and friends!"
"Not any more." The witch waves her hands and the crowd blinks in confusion. "Now then, little boy. What's your name and where are your parents?"
The boy blinks. "Uh, I'm Joey. And that's my mommy and daddy down there." He points to a couple who up until that moment had been childless. Now they nod and smile, because Joey is indeed their son and always has been.
"And you, young man?" She turns to the strapping 25 year-old, who looks puzzled.
"Uh, I ain't got no family. I'm just passing through."
Illusia smiles. "And what is it each of you want?"
The child shrugs. "Uh, a pony?"
The young man scratches his head. "I want to find a job where people don't tell me what to do."