Young Money teenage rapper Lil' Twist links up with his pal Justin Bieber for this song, which finds the pair reaching out to "every girl in the world" as potential girlfriends. Twist told MTV News how they started collaborating with each other: "Me and Justin, we actually met through a mutual friend, and after that, we got real cool, actually," he said. "[We] started working in the studio, sending stuff through the MacBook and everything."
The lyrics for "Mary, Did You Know?" were written by Christian singer and comedian Mark Lowry, after his pastor asked him to write a Christmas musical for their church. Southern gospel musician Buddy Greene later added music to his words.