These celebs’ major hair malfunctions will make you wonder what they did to piss off their stylists, if they even have one.

Christina Aguilera has sported a lot of questionable hairstyles over the years — from multicolored highlights to crazy cornrows — but her current bleached-blond bob loses major points for lack of originality since it’s pretty much a rip-off of Lady Gaga‘s signature style. And just like lace face masks and circle lenses, there are certain things only Gaga can get away with.

Technically, Britney Spears‘ worst hair moment of all time was when she decided that she didn’t need any and shaved her head. Sadly, things don’t seem to have improved much since her hair has grown back. The pop star constantly steps out with ratty extensions that make her look like she has the mange.

At first we thought that Mena Suvari was wearing some kind of strange hat, but after a closer look, we can confirm that the thing sitting on her head is indeed her hair. And the worst part: The updo is French braided up the back, prom-style. That’s two major hair offenses rolled into one horrifying look.

It’s hard to believe that there was a time when we totally coveted Mischa Barton‘s mane. Those sun-kissed highlights! Those glossy waves! If the O.C.’s Marissa Cooper, could see the star now, we’re certain that she would like, totally barf, over these fake-looking, Barbie-esque extensions.

When Kelly Osbourne first dyed her hair lavender we actually thought it looked kind of cool. But now that the color is more gray than purple (not to mention those lunch lady-inspired curls), the only place that this look would be considered trendy is on a box of Betty Crocker.

In all fairness, Katherine Heigl had to dye her gorgeous blonde hair dark brown for a movie role, so we won’t rag on her about the color. But what’s her excuse for this ’80s-news-anchor-meets-politician’s-wife bouffant? We can only imagine how many cans of hair spray had to die to achieve this helmet hairdo. Aqua Net® Professional Hair Spray anyone?

As the mother of four children, it’s entirely possible that Heidi Klum didn’t have enough time to blow-dry her hair before running to this red carpet event. However, we have a very bad feeling that her wet-looking, slicked-back style was done intentionally.

Taylor Momsen‘s Rapunzel-goes-Goth extensions are so long and straggly, we actually miss that weird mullet cut she used to have (and that’s saying a lot). Oh, and no one was even remotely surprised when the wannabe rock star recently told mtv.com that she doesn’t brush her hair.

If you stood on Cassie‘s left side, you would assume that she had a lovely head of hair. And you would be half right. The singer shaved one side of her head, writing on Twitter “sometimes in life you need a change.” Yeah, that’s what a few face-framing layers or some pretty highlights are for.

At first we thought that My Bloody Valentine actress, Jaime King, was headed to a costume party, where she dressed up as some sort of alien with crazy hair. But she actually sported these finger-in-the-socket curls to an awards show. Yikes!

We’re usually fans of Rihanna‘s envelope-pushing style, but we just couldn’t get behind her cherry Kool-Aid colored, half-shaved bowl cut. (Just writing that made us woozy.) Luckily, her hair is starting to grow out and our fingers are crossed that her next look won’t be quite as aggressive as this one.

Maybe arriving at the London premiere of The Back-Up Plan with her hair styled in a way that can only be described as “fancy bird’s nest” was Jennifer Lopez‘s misguided attempt to distract people from the rom-com bomb.

Who do you think sported the worse celebrity hair?

I am admittedly not fond of Katherine Heigl. Her diva ways are, to me, ungrounded. Despite my distaste for her work, I have to admit that I love her look for the premiere of “The Killers.” From the neck down she looks fab. I love the sheath dress and those shoes would look great with my favorite pencil skirt! The dress is by Victoria Beckham believe it or not!

Now, from the neck up and I immediately thought of the late Dixie Carter as Julia Sugarbaker in one of my favorite classic shows, “Designing Women.” The look was great for the 80’s, but this attempt to give a nod to retro looks failed for me. The color suits her, but blonde is more complimentary for her tones.

In my travels I found that people either love Katherine Heigl or aren’t exactly team Izzy. The Grey’s Anatomy star is no stranger to drama on and off set. She has been embroiled in rumors of an onset war that involves the writers for the show. Currently the word is that she has already filmed her last seen for the doc drama and is now free to focus on films or her new baby.

Perhaps in celebration of her freedom or maybe even a new film, Heigl has ditched her blonde locks for a brunette do. If you recall, she first popped onto the scene with super long hair that was slightly curly and the envy of us all.

Katherine continues to encourage my envy. She can bounce back and forth between blond bombshell and sultry brunette with ease. So it is no surprise that in a poll conducted by People magazine, the two colors received nearly equal votes. Blonde is currently sitting at 52% preference.

These beauties clearly should have checked themselves, prior to stepping out anywhere.

10. Katherine Heigl & Her Over-Bronzed Cheeks

Katherine stepped out at the Oscars red carpet looking like she had too much fun in the sun bathroom. One of her handlers should’ve let her on to the fact that she was overdoing it on the bronzer and the blush. Poor thing, it’s caked on ala Tammy-Faye Bakker.

9. Blake Lively’s Bad Chest Concealer

Blake hit up Elle’s 16th Annual Women In Hollywood Tribute with a spotty looking chest. She was attempting to cover up some pimple action with concealer that didn’t match her skin tone. Is she a victim of poor lighting?

8. Sophie Monk’s Over-Plumped Lips

Really is anyone born with lips this size? Well, unless your name is Angelina Jolie or Scarlett Johansson. Sophie showed off her extra plumped up lips ala Lisa Rinna for most of 2009. We’re scarred. While she’s a pretty girl, those lips should not be on that face. End of story.

7. Cameron Diaz’s Sweaty Armpits

Cameron showed off some extra sweaty pits at a red carpet event this year. She looked radiant otherwise, with her perfect hair and makeup. It’s too bad that she radiated heat in this zipped-up gray dress. We still love her, though.

6. Jessica Simpson’s All-Around Blush & Under Eye Concealer

Jessica has been rockin’ the natural look lately, after being seen on the red carpet at her sister’s “Chicago” premiere with a bit of an application problem. She seemingly had her blush blushed all over her face and her under-eye concealer was way too light. And that’s not even mentioning those failtastic smoky eyes.

5. Sienna Miller’s Sun Damage

Obviously Sienna loves to play around on the beach while attempting to give her skin that perfect glow, but it looks like she baked too long, possibly causing damage to her pail skin. Also of note is how it appears that she just waxed underneath her nose. Bad combo.

4. Nicole Kidman’s Too-Powdered Look

Nicole stepped out of the house thinking she looked somewhat normal. But when the snappers caught her on the red carpet, their flashes showed off some poorly applied powder. Either that, or she dipped her face in some coke on the way over.

3. Isabel Lucas’ Terrible Tan and Haphazard Highlights

Isabel looks like a reject from a 1960′s “Star Trek” episode. She has obviously abused the can of tanning spray and the lighter eyeshadow reflects that terribly. Her ultra blond locks wash her out and these extensions are just going overboard. She’s a natural beauty, but she’s more suited to darker hair colors.

2. Lindsay Lohan’s Whole Face

Lindsay has had a rough life 2009. First she plumped up her lips and then denied it. In her older films, you could tell that Lindsay had thinner lips, but lately she looks like a 40-year-old caricature of her former self.

1. Kim Kardashian’s Sunburn

Kim laid out in the sun way too long and got this cancer inducing sunburn. This is the type of burn that hurts to even move around with. And you gotta love the outline of her sunglasses. It makes you wonder why she posted this on her blog in the first place? Maybe so everyone could call her dumb for laying out in the Mexican sun without protection?

Get this woman a doctor! Or at least a makeup doctor. It’s hard to imagine Katherine Heigl as a plain Jane, but without makeup (or a comb-out), the “Grey’s Anatomy” star looks like she’s dragging to the end of a resident’s 80-hour rotation.

Even without the glittering earrings and sleek up-do, this classic makeup combo works for real life or red carpet.

Using a soft black eyeliner pencil, gently smudge your lower rim, then repeat the technique on the upper lash line. Blend outward to create the smoky shadow look. Swipe a peachy-coral blush – a stunning choice for blondes – over cheekbones, and finish with a neutral sienna lipstick.

Face Chart by Tarek Abbas, National Makeup Artist for Lancôme

Related: Eva Longoria, Gwyneth Paltrow, Jennifer Garner, Madonna, America Ferrera

Here we find them at their best — and hair-raising worst!

Here, Katherine Heigl shows us how to do waves the right way with her old Hollywood glam look. But with too much product her locks look dingy — not to mention straight out of “There’s Something About Mary!”

Please tell us this mullet-inspired chop job is for a movie role! Hopefully Jada Pinkett Smith‘s hair will grow out soon to our preferred look — shiny and sleek.

Only Bo Derek could be a perfect “10″ in cornrows. We’re glad Christina Aguilera has traded her Dirrty ‘do for Marilyn Monroe-inspired platinum blonde waves.

No wonder Victoria Beckham started a blunt bob trend in Hollywood — it suits her perfectly. In her stodgy up-do, however, she looks like she’s taking her reputation as an ice queen a little too seriously.

How did L.A.’s biggest party girl end up with a soccer mom haircut? Luckily, Paris Hilton soon grew her ‘do into a perfectly flirty asymmetrical bob.

Katie Holmes proves that all the money in the world can’t buy perfect hair. Mrs. Cruise’s tousled tresses look childish next to her signature sharp bob and bangs.

She’s known for her eccentric style, but Mary Kate Olsen‘s Marc Jacobs’ headband makes her look more aerobics instructor than fashion icon. MK should stick to long, messy blonde tresses for black tie events instead.

Hey, Fergie — Bret Michaels wants his look back! The Glamorous star looks the part when she wears her honey hair wavy and free.

Scarlett Johansson‘s super-poufy beehive doesn’t create much buzz, but her blonde hair looks gorgeous in cascading waves.

We didn’t realize that Alicia Keys was such a fan of the Coneheads! The No One singer looks much better in her natural curls.

Ever since Evan Rachel Wood began dating rocker Marilyn Manson, her style has taken on his goth tastes. We, however, prefer the original.

CELLCOSMET ULTRA VITAL SKIN CARE CREAM

Ever wonder how Jennifer Aniston keeps her skin so flawless? The actress relies on Cellcosmet’s Ultra Vital Cream – and she’s not alone.

Leading ladies from Charlize Theron to Katherine Heigl swear by the Swiss brand, which uses a world-renowned tradition that’s been a favorite of screen sirens since the ’30s.

• Cellcosmet Ultra Vital Skin Care Cream – Enchante’ – $120 – $280

1. Start with a tinted moisturiser to cover up any small imperfections. We recommend MAC’s Select Tint.

2. Go easy on the eyes. Just a lashing of mascara should do the trick. Try Lancome’s Hypnose.

3. The secret to the cheeks is to go very light. Literally, one quick flick of the blush brush (we love Clinique’s Blushing Powder Blush Limited Edition) will be enough. You want the cheeks to have shape, not necessarily colour.

4. Finally, the lips. Go all out here with a gloriously rich and creamy red. Outline the lip with a nude lip pencil and then fill in with lashings of lipstick. We think Revlon’s Super Lustrous Lipstick is an absolute winner.