"I think I want to play with you" Chris says to the sheep dog.
The dog looks a little sad as Chris says that, then replies "OK then, come on in."
Chris cautiously steps over the raised barrier into the enclosure, a flash of light blinding him. With second thoughts he turns to go back out but is met by a thick glass blocking the way that he apparently had stepped through but can't now.
One of the boys playing turns and sees Chris has stepped in, yelling out "YES!" and runs over to Chris, sticking his hand out, "My name is Jeremy, I'm so glad you came in and want to play with the dog!"
Chris shakes the boy's hand "Uhh, I'm Chris..." he replies.
The shake complete, Jeremy pulls his hand back and starts stripping out of his tshirt, shoes, shorts and briefs right in front of Chris.
Chris blushes at the sight of the naked 10 year old in front of him, trying to only look at the kids face. "Why did you just strip?"
Jeremy just ignored him, looking down at his own body, watching as his feet start to grow a little, then his balls begin to drop and grow, soft blond fuzz starting to grow above his child size penis.
Chris saw the growth of pubes from the corner of his eyes, drawing him to start at the kids crotch as the uncut penis slowly grew.
"What the hell?!" Chris said in amazement, casually scratching his 25 year old chest, not knowing his chest hair was starting to thin.
"I can't believe I am finally getting out of here!" Jeremy said with a deepening voice as he grew taller, his blond hair starting to darken, his face starting to look different and more familiar to Chris.
Chris' stomach and waist suddenly thinned, loosing the pounds he had gained since he had been 20 and causing his pants to slip to his ankles. "What the?" He said naturally reacting to bend over and pull them back up but pausing as he saw the hair on his legs looked much lighter.
Chris stood back up leaving his pants at the ground and lifting his shirt slightly to look at his stomach, amazed to see the fat had melted back to his 4 pack abs, the hairs there also lighter and thinner. Turning to the glass he looked at his slight reflecting, seeing his hair was also lighter, his stubble almost gone from his face. His face looked like his but different at the same time.
Looking back at the kid Chris asked "What are you doing to me?" His mouth dropping at the sight of the kids further changes while he had been distracted by his own. The kid had to have been 15 by now, taller and more fit, brownish blond hairs up his legs, his penis a decent size for his age, but his foreskin now looking more like a half circumcision. Hairs were starting to grow up to his navel just as a surgery scar appeared right where his appendix was, looking exactly like Chris' own scar. Looking at his face it looked even move familiar to Chris now.
With a smile Jeremy walked up to Chris, the boy now almost as tall as him, easily removing Chris' shirt without resistance as Chris just stared at the growing boy, then dropped his boxer briefs.
"Not too bad, might need a little exercise to get rid of that tummy you had. A decent cock too. Much better than what billy over that used to be, a big fat older guy!" Chris could suddenly recognize the voice as almost his own, his eyes going wide as he snapped out of his stare.
Chris looked back down at his own body, his pubes now the same brownish blond as the kids, his own cock gaining half a foreskin and now looking identical to the kids.
"Your stealing my body!" Chris said as Jeremy grew and Chris shrank to the same height, hairs starting to sprout from the kids growing pecs.
They stared at each other as they passed the few seconds they were both exactly the same, exact twins at 17 and a half, until Chris was watching as Jeremy was growing taller than him, chest hair flourishing as his own dwindled. He watched as Jeremy's foreskin disappeared completely on his thickening cock, while his own shrinking dick finished gaining its protective covering.
Chris's hair continued to lighten as Jeremy's became more and more brown, thickening across his chest and stomach. Chris' own scar disappeared as the last of his light body hair pulled in, cock and balls shrinking, adam's apple pulling in.
Jeremy watched in the glass as his face finished changing into Chris', looking down as his stomach and waist thickened with a little chub, scratching his ass feeling the hairs on it as well.
"You sure were a hairy one! But I like that in a man... Oh yeah, hope you didn't have a girlfriend." Jeremy said before easily lifting Chris' 10 year old body out of his too big shoes. "You won't be needing these clothes anymore."
Jeremy quickly pulled on Chris' old clothes, a perfect fit. Walking up to the glass he turned to Chris' "Off you go Jeremy, time for you to get dressed and go play, you might be here for a while until someone else takes your place. I was in here 5 years, the old Bobby 10."
The new Jeremy just stood in shock as the new Chris stepped back through the glass into the real world, never to see his former body again.