And now, working with the macy's believe campaign. Write a letter and drop it into a believe mailbox at macy's around the country. For every stamped letter, macy's will donate 1 to make-a-wish.... See More
And now, working with the macy's believe campaign. Write a letter and drop it into a believe mailbox at macy's around the country. For every stamped letter, macy's will donate 1 to make-a-wish. Reporter: In march, katie began experiencing neurological symptoms, including a paralyzed tongue. Her doct's diagnose, cancer. It's surreal to hear that your kid has cancer. Reporter: Katie underwent nine rounds of painful chemotherapy. The chemo really tore her up. Just a shock to see your daughter like that. Reporter: Friends, family and her fellow cheerleaders helped katie stay positive. Along with one of her favorite activities, rainbow looms. It would keep her mind off of all of it. Reporter: For her wish, katie dreamed of baking a cake with bud buddy. I want to invite you and your family to come and spend the day with me and my family. Reporter: Katie is overjoyed. Days later, katie is at buddy's shop. Together, they bake a cake. Good girl. Doing good. Reporter: And katie plays a prank. That's really nice. What's up? Katie, what did you do? Reporter: Just like on the show. High-five. Reporter: And one special surprise for her family. Katie, I got one surprise for your brother and sister. We have some sculptures of you guys, right? With her chemo completed, katie is cancer-free. Looking forward to a future at sweet, as her special wish. Thank you, chris. Here is buddy right now. How are you? How are you doing? How are you? Big hugs. I love it. Well, you know we had a little surprise for your family yesterday. So, why don't we unveil it. What do you think? Come check it out. Come look at it. Come on, guys. Come check it out. So, we wanted to sculpt yr brother and sister on a cake with you. And we wanted to just -- I had such an amazing time with katie. And I mean, look at the job she did, george. She's like a professional over there. Perfect. Was it fun? Yeah. And working with make-a-wish They do so many great things for so many great families, like katie and her family. It's an honor and a privilege for me to be here. It touches all of us. And it touched one man over there, dad. What do you think? Unbelievable. Do you like it? It's fantastic. Can barely speak. What do you guys think? How does it look? Amazing. Katie, I have a gift for you in the back. I told you I was going to give you all of the cake decorating stuff. You wanted your own little basket so you can do cake boss at home. All of the good that make-a-wish does, until you really see it, until you're there and you experience with the families, that money goes to such a good place because these kids deserve it so much. They do. And so much happiness. To see that smile. Thank to everybody for their support. We love katie. And merry christmas to everyone. Thank you, buddy. We want everybody at home to learn how they can send a letter to santa, as well at home. Go to goodmorningamerica.Com on yahoo! And 900,000 has come in so far.
This transcript has been automatically generated and may not be 100% accurate.