These kindergarteners surprised their school's deaf custodian by signing the entire 'Happy Birthday' song.

When Molly Reeser was a student at Michigan State University, she took a job mucking horse stalls to help pay for classes. While she was there, she met a 10-year-old girl named Casey, who was being treated for cancer, and — because both were animal lovers — they became fast friends.

Two years later, Casey died of cancer.

"Everyone at the barn wanted to do something to honor her memory," Molly remembers. A lot of suggestions were thrown out, but Molly knew that there was a bigger, more enduring way to do it.

"I saw firsthand how horses helped Casey and her family escape from the difficult and terrifying times they were enduring. I knew that there must be other families who could benefit from horses in the way she and her family had."

Molly approached the barn owners and asked if they would be open to letting her hold a one-day event. She wanted to bring pediatric cancer patients to the farm, where they could enjoy the horses and peaceful setting. They agreed, and with the help of her closest friends and the "emergency" credit card her parents had given her, Molly created her first Camp Casey. She worked with the local hospital where Casey had been a patient and invited 20 patients, their siblings and their parents.

The event was a huge success — and it was originally meant to be just that: a one-day thing. But, Molly says, "I believe Casey had other plans."

One week after the event, Molly received a letter from a five-year-old boy who had brain cancer. He had been at Camp Casey and said it was "the best day of his life."

"[After that], I knew that we had to pull it off again," Molly says. And they did. Every month for the next few years, they threw a Camp Casey. And when Molly graduated, she did the most terrifying thing she had ever done and told her parents that she would be waitressing for a year to see if it might be possible to turn Camp Casey into an actual nonprofit organization. That year of waitressing turned into six, but in the end she was able to pull it off: by 2010, Camp Casey became a non-profit with a paid staff.

"I am grateful for all the ways I've experienced good luck in my life and, therefore, I believe I have a responsibility to give back. It brings me tremendous joy to see people, animals, or things coming together to create goodness in a world that can often be filled with hardships."

Camp Casey serves 1500 children under the age of 18 each year in Michigan. "The organization looks different than when it started," Molly says. "We now operate four cost-free programs that bring accessible horseback riding and recreational services to children with cancer, sickle cell disease, and other life-threatening illnesses."