While battling bone cancer for the third time in four years, 13-year-old Damon Billeck looks to Captain America for motivation. When the cancer returned last January, the doctor asked the young San Antonio native if he understood what was happening to him. Damon's father, Brian Billeck, said Damon responded with, "yes, I can do this all day," quoting a line from "Captain America: Civil War." Brian tweeted his son's response and tagged Chris Evans, the actor who plays Captain America in the "Avengers" movies, which Evans retweeted. Several months later, after Damon fell into a coma from a trial medication, Evans sent out a message to all his followers to keep Damon in their prayers, his father explained. Damon is now living in Houston shelter for cancer patients, and is facing growing tumors. But on a January 2018 snow day, he thanks Evans by sledding down the hospital's parking garage roof.