TMZ unearthed photos of a completely naked Justin Bieber holding an acoustic guitar in front of his junk as he serenades his grandmother for Canadian Thanksgiving last October. Apparently he "slept in a little too late on Thanksgiving morning [and] woke up after hearing family and friends stirring around the house — so he thought he'd prank 'em by grabbing his guitar and playing a naked set," at which point "everyone in the home was cracking up."
Conclusion: The Biebers are what we call a "Naked Family," the kind in which family members are preternaturally comfortable with one another's nudity. Naked Families are either highly evolved and impossibly mature (It's just the human body, what's to be ashamed of?), unabashedly crude and deeply juvenile (I'm mooning you!), or both. Naked Family antics tend to terrify members of Clothed Families. Their terror, in turn, makes members of Naked Families roll their eyes and/or laugh aggressively.
Conclusion, Part 2: Canadian Thanksgiving is much wilder than ours. Click here for the pictures of Bieber's tiny granny pursing her lips as he strums his musical loin cover.