After listening to Simon explain the many possible changes the machine could make, Jay thought for a minute. Looking at Bryan, who was flexing in the mirror, he gulped.
"Well, if he's going to be so big and old, I want to try the other way. Can you make me younger? To about eight?"
Simon was a bit surprised, but nodded. As he typed in the adjustment, Bryan sat down to watch with interest. The beam soon shot out and washed over Jay's body, making him tingle and swallow loudly as he wondered whether it was a good idea.
Jay's clothes began to feel baggy and heavy as he felt himself shrinking, his growth spurt reversing as the room around him seemed to grow larger and larger. His throat tingled, and as he touched it, his adam's apple shrank and pulled inwards, becoming invisible.
His square, mature jaw softened, brown hairs receding and pulling inwards as his skin grew smoother and more childlike, the hair on his head lightening in hue, returning to the lighter blonde he had as a kid. Pulling up his unwearably baggy shirt, he saw his pecs and abs smooth over as his chest hair vanished, leaving him slim and smooth and immature.
The bulging muscles on his arms shrank and left him thin and scrawny again, his hands and feet shrinking as his body shrank more, leaving his head slightly larger proportionately. He whined and hopped from one foot to the other as a tight feeling ached in his pants, puberty reversing.
Finally, Jay was standing in front of the other two as a 4'10 little kid again. Simon opened up his cupboard and rooted through his old clothes, finding something that would fit Jay, before tossing him some of his old kid's clothes. Blushing, Jay stood in the corner and pulled off his baggy attire, before putting on a pair of power rangers briefs, blue shorts, and a digimon-themed t-shirt.
Bryan shrugged and rubbed his hairy chest. "Man, I dunno why you'd want to be a kid. Being a big man feels great!" Jay stuck out a tongue at him. "You're old enough to be my dad, Bryan. Nothing wrong with being a kid again."