Unbeknownst to Jon and Karyn, Sarah had gotten the rock back in her hand and was watching the resulting carnage. She began laughing. "Now for a bit more fun. I wish that Jon would would become a girl that's a sexy bimbo."
Jon turned into Jennifer, a sexy bimbo. But since neither he or Karyn heard the wish, both of them thought that Jon (or rather Jennifer) had always been that way. And, of course, because of one of Sarah's previous wishes, Jennifer (even though she was a girl) was obsessed with large breasts.