Immediately after Karyn's change happened, Jon regretted their decision to leave the mall and come back to the school (which led to Karyn becoming a cheerleader), but after spending some time with the new Karyn, he realized that maybe the change wasn't such a bad thing after all. Yes, she acted a little different, but deep down she was the same Karyn he always knew.
And it was even better yet, since this version of her seemed to be interested in him. Their long-lasting kiss was proof of that.
Jon had been thinking of using the stone to change her back to normal. But now, he was thinking of leaving things the way they were.
