4. Kara DioGuardi for Women's Health

First off, I didn't know she's 39 (!). And secondly, I didn't know she helped write some pop songs I actually like. One example is "I Do Not Hook Up" by Kelly Clarkson. Here's what Kara had to say: “I wrote this with Katy Perry on my kitchen floor. Originally the line was ‘Keep your thing in your pants, your heart on your sleeve,’ which I really liked. But Kelly hanged it to ‘Keep your head in my hand and your heart on your sleeve." Okay, I can just imagine Katy sitting on a kitchen floor somewhere and writing a song. How fun!