"Mistletoe" by Justin Bieber is originally in the key of D major. Released in 2011 as part of his Christmas album "Under the Mistletoe," the song was written by Nasri Atweh, Adam Messinger, and Justin Bieber himself. It became a commercial success, charting in several countries and becoming a staple during the holiday season. The song's catchy melody and romantic lyrics capture the festive spirit of love and celebration during Christmas. Interestingly, "Mistletoe" marked Bieber's first Christmas-themed single and showcased his versatility as an artist beyond his usual pop style.