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12. ''TIMING IS EVERYTHING'' (Season 1, Episode 10)/
''OUT WITH THE OLD'' (Season 2, Episode 1)
While it may be every wannabe fashionista's dream to go to Paris (to work for a major magazine, no less), Lauren turned down the ''chance of a lifetime'' for a casual summer at the beach with her then boyfriend, Jason. But, of course, the relationship did not make it past Labor Day. Teen Vogue boss Lisa Love made sure to rub this in Lauren's face (''How did that work out for you?''), dubbing her ''the girl who didn't go to Paris.'' As a result, Whitney stepped in and later got a job with Teen Vogue, People's Revolution, DVF, her own fashion line, etc.
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11. ''WHEN YOU LEAST EXPECT IT'' (Season 2, Episode 2)
Lauren went on a date with ''Spencer's friend'' Brody Jenner, which opened the floodgates for nearly every lady on The Hills to have a short-lived romance with the failed Prince of Malibu. Playing the role of Lauren's crush finally gave him reason to stay in the limelight, and his onscreen antics have given him the reputation as one of young Hollywood's most notorious playboys.
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10. ''WITH FRIENDS LIKE THESE'' (Season 2, Episode 7)
After flirtation between Brody and friend Jen Bunney crossed the line, Lauren felt betrayed and vowed to eliminated any ''shady'' friends from her life. This led to the reemergence of Lo Bosworth and the slow fade-out of Jen (nice knowing you), and proved that no one wants to feel the wrath of Lauren Conrad.
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9. ''DREAM BOY, DREAM JOB'' (Season 4, Episode 18) Whitney gets an interview with Diane Von Furstenberg in NYC and meets Australian rocker Jay, which sets up the premise — and drama — of her spin-off The City. Truly the only easygoing, nondramatic one of the bunch, Whitney's departure for the East Coast proved that there was life beyond Les Deux. Her exit left Lauren to fend for herself amid a slew of incomparable replacement friends with concocted drama, all of whom never quite filled Whitney's elegant and laid-back shoes.
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8. ''TRUTH AND TIME TELLS ALL'' (Season 3, Episode 3)
Audrina begins seeing an ex, Justin, who masks his own fear of commitment, responsibility, and overall human decency by spouting crazy faux philosophical babble. As soon as he said ''Truth and time tells all,'' we had our first glimpse of the insanity that is Justin Bobby. And three seasons later...we're still trying to figure out what that means.
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7. ''DON'T ACT INNOCENT'' (Season 4, Episode 8)
Spencer verbally abuses Heidi's mom, Darlene (his mother-in-law to be?!), over lunch, causing her to break down in front of her daughter. It was one of the most heart-wrenching moments of The Hills as her mother's tears showed the extent of the Spencer-Heidi relationship and its true effect on others.
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6. ''YOU KNOW WHAT YOU DID!'' (Season 3, Episode 1)
Though Lauren and Heidi began the show as roommates and best friends, a lot can happen in two seasons. After Lauren believed Spencer started some nasty rumors about her, the girls had a very loud and public fight at Frankie's birthday party. After the argument and many low blows — ''Heidi, you're brainwashed!'' — it was clear that their relationship would never be the same.
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5. ''SOMETHING HAS TO CHANGE'' (Season 4, Episode 5)
Three?s a crowd. When the girls moved in together, Lauren's best friend from Laguna (Lo) and her new best friend in L.A. (Audrina) just couldn?t seem to make it work. Lauren was stuck in the middle, and after suffering from bouts of the silent treatment and an awkward birthday party, she and Audrina had a dramatic confrontation (reminiscent of her talks with Jen Bunney and Heidi?). It wasn't pretty — tears were flowing and mascara was running — but it ultimately led to resolution. Despite saving a friendship, it provided foreshadowing that the end of Lauren's tenure on The Hills was quickly approaching.
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4. ''SOMETHING OLD, SOMETHING NEW...'' (Season 5, Episode 10)
Lauren swallowed her pride and attended Speidi's wedding, opting for a low-key entrance and exit, which would be her last appearance on the show. The presence of Kristin Cavallari in the church set the stage for the new era of The Hills, in which the ''man-eater boyfriend-stealer'' wreaks havoc on everyone's lives. While Cavallari can play the bitch role perfectly (and lacks enough class), The Hills never felt the same without Lauren as our heroine.
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3. ''BACK TO L.A.'' (Season 3, Episode 20)
Kelly Cutrone's cameo — hiring Whitney at People's Revolution (''You're basically making a deal with the devil'') — resulted in instant infamy and led to a supporting role on The City and her very own reality show, Kell on Earth. She's arguably the one Hills cast member having the biggest moment right now, as her best-selling memoir, If You Have To Cry Go Outside, has become a mantra and a guide to all the mini-power girls in training. She's not going anywhere, and we wouldn't have it any other way.
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2. ''OUT WITH THE OLD'' (Season 2, Episode 1)
When seemingly wholesome Colorado girl Heidi Montag started dating this L.A. pretty boy Spencer Pratt, nothing between her and best friend Lauren would be the same...and unfortunately, since they got together, nothing has been the same for mankind, either.
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1. ''PUT ON A HAPPY FACE,'' (Season 6, Episode 1)
It would have been more of a shock to viewers had she not appeared on the cover of several magazines prior to season 6, but Heidi's big reveal to her family was still must-see TV. Making her first trip home to Colorado post-plastic surgery, Heidi endured confused looks and tough love from her family, who couldn?t understand why she would put herself through that much pain. As she struggled to talk at a normal decibel and finish chewing her dinner, The Hills became much more real and much, much sadder.