'x factor' 2010 band faced female admirer half naked.
One Direction was stunned to find a fan in their dressing room while they were getting changed.
The 'x factor' 2010 band were using a New York gym when Liam Payne came face-to-face with an admirer while he was stripping down.
Apparently she managed to slip past bodyguards as they were busy holding back an eager crowd in the city.
A source told The Sun: ''Liam was stunned when he saw her in the changing room - he couldn't believe she'd got past security.
''For one thing, he was in the middle of getting dressed and had no idea what she was going to do, as their fans in the US are mad.''
However security was soon alerted and the female was escorted out by minders.
Reports suggest he he'd seen their cover of it online and helped them carry out the performance but the film star embarrassingly forgot Zayn's name.