Zayn Malik and Liam Payne decided it was a good idea to show off Harry Styles's body during their Chicago concert on Sunday.
One Direction were in the middle of their No 1 hit What Makes You Beautiful when Zayn, 19, and Liam, 18, stood behind Harry and ripped open his white shirt.
The crowd broke into deafening screams as Harry, 18, struggled to button up his top and keep his chest covered.
The pranksters later gave each other a high five and Harry a pat on the back.
'Just got to chicago! Tired maaaannnnnn! Cya tomorrow!' Niall Horan, 18, Tweeted before the gig on Sunday.
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