They scored a top-five hit with their "Airplanes" collaboration, but B.o.B and Hayley Williams had never met in person ... until now.

A rehearsal for their 2010 MTV Video Music Awards performance Saturday (September 11) finally united the pair, who recorded their vocals separately and shot a video for the song at different times.

"Whoa, hi!" Williams said to B.o.B as he ran across the stage to embrace the Paramore frontwoman.

Williams and Bobby Ray were actually onstage together while "Airplanes" blasted through the Nokia Theatre speakers, but the lights were turned down and something blocked her view of the rapper.

"Where are you guys?" she asked.

B.o.B spotted Wiliams, also his labelmate, and ran toward her. "We finally met for the first time," he said, turning to the camera excitedly. "I hope I don't mess up."

"I'm gonna trip and fall," Williams said about their big performance. "Catch me, please!"

Then a stage manager broke up the meeting as the stars had to get back to rehearsing the number. They later exchanged numbers, and Hayley offered to join B.o.B at a performance in Los Angeles later that evening, if she can make it.

After a long delay, they had a happy ending.

The 27th annual MTV Video Music Awards will be broadcast live from the Nokia Theatre in Los Angeles on Sunday. The party starts with MTV News' VMA Pre-Show at 8 p.m., followed by the main event at 9 p.m. ET/PT.