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.