Proof Celebrities Have a Heart

From the video description:

Zach Sobiech is 17 years old and diagnosed with osteosarcoma, a rare form of bone cancer that takes the lives of a large percent of its childhood victims. Given only months to live, Zach turned to music to say goodbye. His song "Clouds" spread, and soon, Zach's message was heard across the country. We wanted to help Zach spread his message, and bring awareness to increase support for finding a cure. So, we asked our friends to help out...they did.