What's Her Best Hair?

The action star does a Transformers-worthy red-carpet switch-up of her own on the MTV Movie Awards red carpet in ‘09! The previous year, she had gone for stick-straight layers, but slicked back the top and let the ends trail in loose waves for this time around.

The former Hills star sends her soft waves packing, adding chunky texture and extra inches on the MTV Movie Awards red carpet.

For over a year Nicole’s made pale blonde her signature look, but the actress returns to her red roots while filming in N.Y.C.

Everyone has their ups and downs – and the Heroes star takes hers in stylish stride, trying tousled waves at the Spike TV Guys Awards, then pulling her hair into a sleek updo at the MTV Movie Awards.

Forget that classic bob the Oscar nominee wore at the Academy Awards! For the MTV Movie Awards, the actress goes rock ‘n’ roll, cutting her hair into a choppy, spiked style.

The designer gives a jagged edge to her long blunt bob, adding choppy long layers for a film premiere in Hollywood.

Taking her look from glamorous to chic, the Oscar winner straightens her waves into a polished bob.

The actress goes ’80s-sleek at the MTV Movie awards by slicking back her blonde hair, before going wild the next night with tousled layers for a Hollywood film premiere.

It was a weekend of whirlwind beauty for the 90210 star, who attended the Chrysalis Butterfly Ball with a striking bouffant-top updo, which she traded the next night for old-school Hollywood waves at the Young Hollywood Awards in Santa Monica.

The famously dark-haired star adds summery blonde highlights for the Monte-Carlo Television Festival.

“I cut it yesterday,” the Disney star told PEOPLE.com about her new highlighted bob. “I was sitting down in the chair, and I was going to ask for the same thing: little extensions, curling it, long.” But on the spur of the moment, she says, “I just cut it – cut it off! It feels good.”

The supermodel proves just how sexy a bob can be at an event in her German homeland, before trying a summery updo at a charity event in L.A.

For months, was all about soft waves. But she’s taking summer’s warm weather in stride with more natural, ringlet curls.

The actress highlighted her chestnut locks by letting her hair down at the Sunshine Cleaning premiere, then pulled it back into a sleek ponytail to show off new red hair at a charity event in N.Y.C.

hit the premiere of The Ugly Truth with brown hair that set off her dark eyes.

Taking Hollywood’s hair-shaving trend to bold new levels, debuted freshly shorn sides that added edge to her summertime look.

“Here’s my new haircut by Kiyah Wright!:) we teamed up!:),” the singer Tweeted this week of the short style that replaced her signature long tresses.

entered the White House with a long, classic bob – but faked a shorter tucked-under style at a music event this week.

While promoting Transformers: Revenge of the Fallen in Germany, went for major sex appeal with a long slick ponytail. But for the Armani Privé couture show in Paris, the sultry star goes for Old Hollywood glam with face-framing soft curls.

trades in her dark brown locks for a new tousled light blonde do.

Changing hairstyles is all in a day’s work for the Heroes Panettiere starts the day with pin-straight platinum locks for an appearance on MTV, only to arrive at the evening screening of I Love You, Beth Cooper sporting loose waves and deep side part.

The may have spent months with honey blonde highlights in her light brown hair, but at a fashion party this week she debuted a new red tint.

While on set as Gossip Girl’s new Queen Bee, adds length to her signature shaggy do with long blonde extensions done in a half-up style.

The gave up her signature hairstyle for a long brown bob – but only for the day while posing for a magazine. “I got to wear a brown wig all day,” she tweeted. “It [was] fun Kinda like playing dress up.”

You might be used to seeing with tousled auburn locks, but for her new role as singer Joan Jett, Kristen dyed her hair black and went for a choppy style that shouts, “I love rock ‘n’ roll!”

The hit the MuchMusic Awards with a tucked-under bob, which, she tweeted, was all about “channeling Marilyn Monroe.” But days later at a product launch party in Beverly Hills, she was back to her trademark lanky locks.

The abandons her natural red hair for newly platinum tresses.

The departed from the dark auburn hair that she wore for months and tried out a softer strawberry blonde look.

For weeks, the rocked dark brunette locks, but quickly went back to her signature blonde.

“I. just. wanted. to. be. free. from. the. bondage. that. black. women sometimes. put. on. themselves. with. hair.” the singer Tweeted after she removed the blunt-banged wig she’d worn to an event the night before and showed off a natural, closely-cropped do on the streets of L.A.

The Beautiful Life’s gives herself a beauty makeover, darkening her hair from chestnut to deep brown.

The 90210 beauty chops off her wavy locks to create a softly layered bob.