Gabe Saporta: Leighton's Really F-ing Cool

Cobra Starship fans got a special surprise at last night's concert in NYC's Nokia theater when Gossip Girl star Leighton Meester not only made an unexpected appearance, but also joined the band onstage to sing with them on "Good Girls Go Bad."

"It was awesome," Starship frontman Gabe Saporta told OK! at the show's after party at NYC hot spot 1Oak where guests enjoyed MGD 64 beers and Hornitos tequila cocktails. "It was a monumental show for us, because playing in New York is always awesome... but more importantly, Leighton sang with us on “Good Girls Go Bad.” And since that song has been recorded it went top-five, sold a million copies… We’ve never performed it together. Never ever ever. Today was the first time we did that."

And while one might shrug off the idea of an actress like Leighton attempting to cross over to rock stardom, Gabe said she's the real deal.

"The girl can really sing. She’s really f**king cool," he explained. "And the thing is, we’re kinda like bad boy rock dudes and she’s a real-life celebrity. And like I don’t give a f**k.

"So sometimes those two worlds clash together and they don’t mesh well. But with her it meshed perfectly. Like she was still very refined and very cool, but she has a sense of humor and jokes around with us and has a great time."