Watch One Direction Cover 'Fresh Prince' Theme -- In Philadelphia, No Less

When in Philly...

One Direction decided to have some fun while on tour in Philadelphia recently: They sang the Fresh Prince of Bel-Air theme for screaming fans midway through their concert.

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Fans, of course, were into it, but the guys only sang the first part, because -- as Niall Horan noted -- "We didn't think that through. We needed to rehearse it."

"I'm going to be president in 2020," Horan then quips.