Child singer Barry Gordon went on to an acting career, most notably in the Broadway and film versions of "A Thousand Clowns" as a kid, and then to many guest TV appearances as an adult. I believe he was also president of the Screen Actors Guild for a time. He'd be in his mid-50s now.
Alvin and the Chipmunks recorded "We're Gettin' Nuttin' For Christmas." The classics never die.