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(InStyle.com) -- Stars like Katy Perry and Jennifer Lawrence changed up their hair color and length in 2011 and achieved dramatic results.

See the most memorable hair transformations of the year.

The "Gossip Girl" star went auburn in late April for her role in the upcoming film "Hick." In June, Lively lightened her strands back to blond.

"I love it," she told InStyle.com on her ever-changing 'do. "When I play a character I love to completely transform, and changing up my hair color is a way I feel like I can disappear behind them."

Katy Perry went back to her blond roots in July, then revealed a new lavender hue at the VMAs in August.

"It was such an exciting challenge to custom-create Katy's color for the VMAs," her colorist Rita Hazan said. "She is always willing to take risks to achieve a groundbreaking look."

The "Glee" actress cut her blond waves into an edgy shag in August.

"It feels more like me than ever," she told InStyle.com exclusively. "I love it! I don't miss blow-drying my hair, I don't miss the maintenance, and it's just fun to switch things up."

In June, Wood debuted her new pixie crop at the "True Blood" season four premiere party in Los Angeles.

Aniston chopped her long layers into a one-length bob while promoting her film "Just Go With It" in February. The cut, courtesy of Aniston's longtime hairstylist and friend Chris McMillan, is the first time she has had above-the-shoulders strands since her famous Rachel shag in the '90s.

Carrie Underwood debuted pitch-perfect bangs that hit just below the brow in late September.

In April, Barrymore traded her two-tone ombre for blazing red.

"We had been talking about going red for a few months, and since Drew has been auburn before, we knew it would look good," her colorist Tracey Cunningham told InStyle.com exclusively. "It wasn't a spur-of-the-moment decision. When Drew changes her hair color, she really commits to it."

History repeated itself in early November, when Barrymore went back to her ombre roots and snipped her strands into a long bob.

For her role as Katniss Everdeen in "The Hunger Games" Lawrence switched her sunny blond for a deep brown in May.