During Saturday’s rehearsal, Mars crooned "beautiful squirrels" instead of "beautiful girls" as he and rapper B.o.B. prepared to run through their hit, "Nothin’ on You."

Later, Mars entertained himself and a few dozen workers inside the Nokia Theatre by singing The Police’s 1978 hit "So Lonely."

"Why are you trying to sing higher than me?" Paramore lead singer Hayley Williams asked playfully over the microphone.

"Sorry," Mars sheepishly responded.

Not to be outdone, B.o.B. chimed in with a few verses from Cee Lo’s expletive-laden new single. Mars accompanied him on piano.

Mars and B.o.B. also beat-boxed between performances of their medley, which also includes the rapper’s "Airplanes" and the rockers’ "The Only Exception."

Mars grew up in Hawaii and is a Roosevelt High School graduate. He also performed in Waikiki as a child.

Williams confessed that she got a little turned around on the show’s expansive, space-age set with its sloping canopies and multiple video screens.

"I thought the stage was over there," she said, running to her spot in front of the band. "I was lost, but now I’m found."

The three young entertainers are among a slate of performers expected at Sunday’s ceremony, including Kanye West, Eminem, Usher and Mary J. Blige.

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On the Net:

http://www.mtv.com/ontv/vma/2010/