I give you the first finished object from my [three] Magic Yarn Ball[s]:
I have green and white yarn, too, and Priscila has informed me that it's perfectly fine if I want to make her a white one for her tree. Don't tell her, but I totally will!
In the very center of each ball was an ornament with candy inside it. In the white ball was also a little slip of paper that said I'd be receiving Knit Simple Magazine for a year ("Happy Birthday!"), and also at the core of the green ball was a small box. Inside the box was a necklace she got in Montreal, and it looks like a plate of sushi. I love it. I wore it today.