Bieber Pulled Nude Prank ... on Grandma Serenaded her wearing nothing but a guitar By Evann Gastaldo, Newser Staff Posted Aug 12, 2013 8:44 AM CDT 22 comments Comments Singer Justin Bieber performs at the Prudential Center in Newark, NJ on Wednesday, July 31, 2013. (Photo by Evan Agostini/Invision/AP) (Newser) – Oh goody, another really gross Justin Bieber story. Somehow TMZ has obtained pictures from October 2012 of the then-18-year-old serenading his grandmother while completely naked. The photos are from Canadian Thanksgiving, while Bieber was at his grandma's home in Toronto; a source says the singer woke up late on the morning of the holiday and decided to prank the family and friends who were already up. With just a guitar covering his you-know-what, he started strumming away while singing, "I loooove you grandmaaaa." Apparently she, and the rest of the guests, found the whole thing hilarious, although she did order Biebs to get dressed. Photos here, if you dare.