Two tip-offs that 13-year-old Joey Russell is a great guy: One, his best friend is a girl, and two, he hates talking about himself. Joey made both points clear recently when he decided to sell his cherished 1912 postcard of the Titanic to help save Kate Shelley's mother, Mary, from leukemia. "I did it," says the shy eighth grader from Havre de Grace, Md., "just because she is my best friend and her mom was in trouble."

He achieved far more than he had dreamed. Joey had hoped the card, bought four years ago at a collector's show for $100 in chore money and signed by a Titanic survivor who died last year, could fetch $2,000 toward the remaining $60,000 needed for a bone-marrow transplant (the community raised $20,000, and insurance covered the balance of the $225,000 cost). Learning of his plan, Rosie O'Donnell invited Joey to pitch his postcard on her April 16 show. Just as he finished, the cast of the Broadway musical Titanic paraded onstage to serenade him ("We think you're such a special kid/deserve awards for what you did!"). Then came the biggest surprise: In a deal brokered secretly by O'Donnell and the Titanic producers, the cast delivered a check for the full $60,000. "Joey is an inspiration to me," says Mary Shelley, 40, a divorced mother of five whose transplant is scheduled for May 18. "He has touched my heart so."

Joey first considered selling his postcard when his parents, Mary and Paul, who run a collector's shop, discussed donating one of their cars to help Shelley. Joey told them: "I've got something that's way more valuable." Kate was moved by her friend's unselfish act. "He's really shy, he's funny, he likes to goof around," says Kate, 14. "But I wasn't expecting this."