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30) Owen chokes Cristina out. Before the pair were married, Owen was wracked with nightmares of his time in the war. His post-traumatic stress disorder was triggered when he thought the ceiling fan was a helicopter and he set out to defend himself against the only "enemy" in range: Cristina.
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29) George gets syphilis. Getting syphilis sucks. Getting syphilis from an enemy? Mortifying. George's ailment was honestly much funnier than shocking, except that it revealed just how many doctors were making house calls on one another.
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28) Meredith's alt-universe. When Meredith dreams of a world in which her mother did not have Alzheimer's, Seattle Grace is turned on its head. Not only is she enemies with Cristina, but she's engaged to Alex, who is actually cheating on her with April, her supposed best friend. Meanwhile, Callie and Owen are married, Derek and Addison are expecting (but it's Mark's baby!), and Richard actually married Ellis Grey. Yikes!
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27) George talks Bailey through labor. Though also quite comical ("George, stop looking at my va-jay-jay!" still kills us), Bailey finally let down her "Nazi" guard and, to her own surprise, learned there's no shame in sometimes being vulnerable.
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26) Owen cheats on Cristina. Owen and Cristina had been struggling through much of Season 8, but Owen dealt with his uncertainty in a shocking and despicable way: He gets drunk and has a one-night-stand with a floozy. After recalling every detail to Cristina, he packs his bags and moves out.
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25) McSteamy comes out of the shower. Though the ladies' jaws hit the floor because Dr. Sloan was (literally) living up to his nickname, this moment was equally effective in capping the once-and-for-all ending of Derek and Addison's marriage.
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24) Cristina loses her baby — on purpose. Distraught at the thought of being a mother, which would severely affect her one and only passion, her job, Cristina decided to abort her and Owen's baby. Owen kicked her out when she made the decision, but after an "Ellis Grey was a terrible mother and it ruined my life" speech from Meredith, he came around, and even held Cristina’s hand through the procedure.
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23) Meredith tampers with the Alzheimer's clinical trial. After Adele scores a spot on the Alzheimer's clinical trial, Meredith tampers with the trial to ensure that she won't receive the placebo. But after Alex outs her in hopes of getting the Chief Resident job, Meredith is fired. When The Chief discovers the sacrifice she made in Adele's name, he takes the fall and steps down from being Chief, after which Meredith is reinstated.
9 of 30 Karen Neal/ABC
22) Alex and Addison kiss. For these two, sexual tension didn't come from making babies, just taking care of them. When Alex showed a rare softer side to the emotionally vulnerable Mrs. Robinson, er, Addison, the tension finally bubbled over.
10 of 30 Scott Garfield/ABC
21) Lexie becomes an intern. The worst thing about blowing off the guy every other woman wants is finding out he's found another girl. Even worse is finding out that she's the younger, hotter sister you never knew and is your new intern.
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20) The plane crash survivors buy the hospital. With Seattle Grace on the cusp of bankruptcy because of the settlement paid to the plane crash survivors, a buyer who plans to run the hospital like a fast-food restaurant steps in. So the hospital won't fall in the wrong hands, Meredith, Derek, Arizona, Cristina and Callie band together to buy Seattle Grace, teaming with the Harper Avery Foundation, who puts Jackson in charge. His first real act: Renaming Seattle Grace to the Grey Sloan Memorial Hospital.
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19) Cristina loses her baby. As the first real consequence of Seattle Grace's residents' inability to resist the forbidden fruit of interns, Cristina suffers from an ectopic pregnancy and loses the baby before telling Burke he's the father.
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18) Meredith and McDreamy hook up, again. What's a prom without some bad decisions? But if you find yourself unable to resist a forbidden romp in an exam room, it's best not to let your underwear end up on the bulletin board the next day.
14 of 30 Danny Feld/ABC/Getty Images
17) Callie gets in a car accident. Just as Arizona proposed, a pregnant Callie went flying through the windshield of their car, kicking off a musical episode. The concept was good in theory, but we'll pass on doctors ever breaking into song during surgery again. Callie's baby survived, and she and Arizona married shortly after.
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16) George and Izzie hook up.Think running off to get married as a way of dealing with the recent death of your father is stupid? Try getting drunk and sleeping with your best friend who is way too eager to take advantage of you.
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15) Adele dies. Bailey misses her own wedding when Adele, who had been residing at an assisted living home for Alzheimer's, is rushed to the hospital. Fortunately, she's able to save Adele during surgery and return to her wedding a little bit late. But when Richard arrives shortly after, he doesn't tell her that Adele has died from a heart attack. As everyone dances, Richard visualizes a hauntingly beautiful shot of himself and Adele swaying to "My Funny Valentine" decked out in wedding attire.
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14) Burke gets shot. Who knew a bullet could reduce the invincible Dr. Burke to an emotional mess with a twitchy hand? More amazingly, the bullet also pierced through Cristina's icy indifference, exposing a rare, unexpected human side.
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13) Seattle Grace floods. As if troubled sex lives didn't distract these docs from their daily cut-and-stitch duties enough, try operating on a patient when the ceiling collapses, flooding the O.R. — and an open body cavity. But hey, since they found the patient's pancreatic cancer during the cleanup, he didn't sue!
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12) Alex and Izzie get married. What was supposed to be Meredith and Derek's wedding turned into Alex and Izzie's nuptials, as they rushed to wed before Izzie died of cancer. Like T.R. Knight, Katherine Heigl left the show in Season 6, effectively ending the marriage.
20 of 30 Scott Garfield/ABC/Getty Images
11) A shooter rampages through the hospital. The husband of a patient who was taken off life support shot his way through the hospital, enabling Grey's to get rid of Mercy West transplants Reed and Charles. Alex, Derek and Owen even took bullets, but there was no doubt they would survive, though the same couldn't be said for Meredith's unborn child.
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10) Denny dies. Even after Izzie foolishly cut Denny's LVAD wire to guarantee that he'd get his heart transplant (a shocking moment in its own right), the poor guy still ends up dead.
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9) George and Meredith hook up. After recovering from syphilis and growing out his hobbit hair, George finally gets a chance with his dream girl, Meredith. Unfortunately for O'Malley, the tears she sheds aren't those of joy.
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8) Kyle Chandler blows up. Anytime you sign on to guest-star on a medical drama, there's always a chance your character could die. But only the lucky ones like Chandler's Dylan get to go out with a dramatic explosion. Two words: "pink mist."
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7) Meredith gets pregnant. Despite being told that it was unlikely she could ever conceive, Meredith discovers she's pregnant and breaks the news to Derek by showing him a T-shirt she got Zola that reads: "World's Best Big Sister."
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6) Burke leaves Cristina at the altar. The couple always walked a bumpy road, but seeing Dr. Yang in a wedding gown almost made the marriage seem possible. Thanks to Isaiah Washington's off-screen antics, we can only wonder what might've been.
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5) George dies a hero. After deciding to enlist in the Army, George dives in front of a bus to save a stranger, rendering him so mutilated that he's listed as a John Doe while being treated at Seattle Grace. It isn't until he scratches "007" into Meredith's hand that she realizes her friend is pretty much a dead man. License to kill turned into license to die — and enabled T.R. Knight to leave the show.
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4) Addison shows up at Seattle Grace. This Season 1 cliff-hanger was just what the show — then a midseason replacement — needed to prove it would be sticking around.
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3) Meredith dies (for a little while). Though this moment probably splits viewers' opinions, there's no denying that it takes some guts to kill off your lead character (even if for one episode). And hey, look, there's Denny!
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2) Meredith and Derek get married. After years of the will-they-or-won't-they, the pair finally made their Post-it vows official by getting married. It wasn't the most extravagant wedding, as it took place at City Hall, but it enabled them to adopt baby Zola.
30 of 30 Karen Neal/ABC/Getty Images
1) The horrific plane crash. In one of the more shocking finales in the show's history, Mark, Derek, Lexie, Meredith, Arizona and Cristina find themselves stranded in the woods after their plane crashes on the way to Boise. Lexie dies after sustaining serious injuries from being crushed by the plane. Derek's hand is severely damaged, leading to a lengthy recovery. Mark dies after they're rescued. Arizona's leg is amputated. Cristina suffers emotional debilitation, which causes her to move to Minnesota upon their return.