If you're a pretty celeb, there's no better way to let The Man (or in some cases, The Academy) know that you mean businss than messing with your looks. For Charlize Theron, it meant gaining weight, but for others, it means shaving your head

In Cameron Diaz's upcoming film, My Sister's Keeper, her character shaves her head as an act of solidarity with her daughter, who suffers from leukemia. (In reality, Cam wears a skull cap for the film.) After watching the trailer, I was so annoyed with myself for thinking that she was pulling some I'm-a-serious-actress stunt here. I was literally in tears at my computer, the film looks so poignant. But wow, Cameron sure made me look.

But that's not to say there's a noble cause behind every celebrity buzzcut. Let's think back...

Sinead O' Connor. "Nothing Compares 2 U" had mass appeal, but her shaved head should have tipped us off that we weren't dealing with your average pop star. After singing her famous ditty on SNL, she ripped up a picture of the Pope.

Demi Moore. After the bomb that was Striptease, Demi needed to do something drastic to prove she still had acting chops. So for her next role as a Navy SEAL in G.I. Jane, she exposed the one part of her we hadn't seen - her scalp.

Eve Salvail. Drop-dead gorgeous models are a dime a dozen in this town. But for this 90s supermodel, a shaved head with tattoo of an antique dragon set her apart from the a-little-too-perfect masses. The fashion pack loved her. (Fun fact: She's actually a New York City-based DJ now.)

Britney Spears. Brit-Brit's self-inflicted buzzcut said more "help me" than "hire me." But it certainly put her in the center of pop conversation.

Who knew that no hair could be such a power cut?