Karyn was the only other person who knew about the rock, so she was the obvious choice. Jon just didn't know how embarrassing it would be to tell her.
Karyn was laughing uncontrollably after she had rushed over to help Jon. "What gave you the idea to wish that?" she asked between giggles.
Jon's face was bright red. "It was a moment of weakness, okay. I just need some help finding out exactly what it does."
"Fine, fine," Karyn said, trying to gain composure. "What do you want me to touch first?"
"How about my hand?" Jon said holding out his right hand. Karyn nodded and held his hand. Jon felt an odd sensation in his chest. He could feel two small mounds underneath his shirt; he looked down and sure enough he had a pair of A-cup breasts on his chest.
However, Karyn didn't seem to notice. "Hmm, it didn't work. Maybe if I did it again."
"Wait! Don't--" Too late. Karyn let go of his hand, then grabbed it again. Once again, Jon felt an odd feeling as his chest gained another cup size.
Karyn noticed them this time; she broke down into another fit of giggles. "I think I found the most interesting one. So, your hand is your chest," Karyn said as she let go and grabbed his hand again, "and every time I touch it it grows a little." Jon's chest grew another size to a C-cup.
Jon pulled his hand back. "Stop that." He became very aware of the new mounds of flesh. He really wanted to touch them, but he knew Karyn would tease him even more. "How about we try another body part."
