As The Early Show correspondent Melinda Murphy learned, parents, kids and staff at a Texas children's hospital have been smiling ever since.
Murphy spoke with one such parent.
"Never, ever, in my wildest dreams could I have imagined that my daughter would get cancer," said Jimmie Garrett, fighting back tears.
For two years, Garrett's daughter, Kerre, battled bone cancer.
Garrett showed Murphy a photo album of Kerre's: "This book's all her. She put this together before she died," he told Murphy.
In it are pictures of the women who made Kerre smile, even on her darkest days: a group of volunteers called Clowns Who Care.
"No matter how bad she was feeling," Garrett recalls, "she always had a smile when they came in, and they brought a lot of joy into our life."
Aiming to brighten the days of sick children, "Clowns Who Care" visits Driscoll's Childrens Hospital in Corpus Christi, Texas, twice a week.
The group was founded by Sinclair, who says, "It's the hardest thing any of us have every done. It's the best thing any of us have ever done." Her clown name, incidentally, is "Mz. Glamure."
She reflected back on how she dreamed up "Clowns Who Care."
"The whole time, I kept thinking, 'I really want to do something to give back if I survive this.' And there was a clown in the hospital and I just loved her. She was darling. And that's the way it started."
So Sinclair, who happens to be a fashion designer and real estate agent, began making the transition, signing up for clown school. She kept that secret from her buddies until the day she graduated.