Glen grinned. "This thing can change me back, right?"
Sam looked at the manual and nodded. "Yeah. sure! I mean, if it can change you one way it can change you back, right?"
"OK. Let's make lots of changes. I wanna be 13, sorta dumb and goofy-looking. Red hair, buck teeth, big ears, and freckles all over. And I wanna be hung like a horse."
Sam grinned. "Dumb, ugly and hung like a horse? You're gonna be a fun brother." He looked over the options. "I think I can work all that stuff into this. Yeah, even the horse part! Wow. They think of everything!" He made the final entries and pressed the button.
The changes started slow, mostly just Glen getting smaller as he dropped from 16 to 13 years old. But when his hair turned red, he blinked and stared at Sam. "Hey! What's happening to you?" The other boy's hair was also turning red, and his face was changing.
"Huh?" Same ran over to the mirror and started as his teeth pushed out and freckles spread over his skin. "Shit! Why am I changing too?"
Glen felt his own face and then gasped at a sudden swelling between his legs. "Oh, fuck!" His pants were too big now, and slid down easily to show the black cock, sheath, and balls of a horse between his skinny boy's legs. The cock was almost as big as his arm!
Sam turned and laughed when he saw the actual horse cock, but then gasped as his own pants got tight. He struggled out of them and gaped as an even larger horse cock and balls pushed out from his crotch.
Glen looked at the machine. "Oh! You set it to make me your brother! So it's changing both of us!" Just then, he blinked and looked confused. Then his expression went blank and he looked down and grinned as he played with himself.
Sam stared a moment. His freind looked like he was mentally retarded - and then he felt his own mind start to slow down. Oh, no! If he got stupid, he'd never be able to change them back!
Sam scrambled over to the device and picked it up. He had to fix things! He had to... Sam looked at the weird thing in his hands, not quite able to remember how it worked. The rooma round him was changing, his isngle bed becoming twin beds with plastic sheets, grade school books and posters and toys more suitable to little kids.