Justin Bieber pranked his grandma while naked and coverd just by his guitar

He's often seen showing off his torso by going shirtless, especially of late.
But Justin Bieber shocked his family when he did the full monty during a bizarre nude prank at his grandmother's house in Toronto during Canadian Thanksgiving back in October 2012.
In photos obtained by TMZ, the 19-year-old is seen covering his private parts merely with an acoustic guitar, jamming out a naked serenade for his granny, Diane Dale.

-I.
source:dailymail