We knew that Rebel Wilson could match the wit of more seasoned comics. What we didn't know was that the Australian actress is capable of a mean cover of ''Turn the Beat Around'' one of her many unforgettable moments in this year's sharp a cappella comedy Pitch Perfect. ''We filmed in Louisiana for three months, and the first month was a cappella boot camp because all of us had to be singing 10-part harmony,'' says the actress, 26. Wilson is realistic about her vocal abilities: ''I don't think I'm, like, a Celine Dion or a Mariah Carey. I don't think I could make it on The X Factor. I could maybe fudge my way through it.'' But for us, her work in Perfect hit all the right notes.