'American Idol' Brittany Kerr -- Hot and Dangerous

"American Idol" cheerleader babe Brittany Kerr is more than a pretty face -- she's a pretty face with a black belt in taekwondo!

Brittany tells TMZ she started studying martial arts in Charlotte when she was 8 (above) -- and earned her black belt after 4 years of kicking girls' and boys' butts. Brit says, "I definitely made some boys cry while sparring ... I had a killer high kick!"

Kerr is now 24 and says she's laid off the taekwondo, but still does some kick boxing to stay in shape.