1 of 20 Scott Garfield/ABC/Getty Images
There's usually only a handful of shows that make the tough decision to kill off an important character. On Grey's Anatomy's sixth-season finale, the show bid adieu to T.R. Knight when George O'Malley died after being hit by a bus. His face was so swollen and cut up, however, that it was only in the final seconds of the episode that George's colleagues realized that he was their "John Doe."
Other examples: Charlie on Lost's Season 3 finale, Kate Todd being shot and killed on NCIS.
2 of 20 Glee
Apparently thinking the birth of a child wasn't inherently dramatic enough already, Glee intercut the delivery of Quinn's to-be-adopted daughter Beth with Vocal Adrenaline's performance of Queen's "Bohemian Rhapsody." (It's a corny sync job: When James St. James exclaims "Mama," so does Quinn, in the throes of labor pains.)
Other examples: Jim and Pam's CeCe on The Office; Phoebe's triplets on Friends; Baby Ricky on I Love Lucy
3 of 20 Trae Patton/NBC
After a season of back-and-forth romantic tension, Community's Jeff and Britta finally gave in and bumped uglies in the middle of the Greendale paintball tournament. In truth, Britta was using sex to beat Jeff in the tournament, but their feelings for one another still haven't gone away.
Other examples: Chandler and Monica get it on in London on Friends, Josh and Donna do it after six seasons of flirty banter on The West Wing. Oh, and David and Maddie on Moonlighting, but let's not talk about that.
4 of 20 Patrick Wymore/The CW
TV loves to teach lessons of tolerance, but more often than not, these same-sex seshes are about titillation, not sexuality. One possible exception: Adrianna (Jessica Lowndes) meets the cool, charming Gia (Rumer Willis) on 90210 and embarks on a wholly typical teenage relationship — sweet, passionate… and short-lived.
Other examples: Marissa and Alex on The O.C.; Katherine and Robin on Desperate Housewives
5 of 20 Jordin Althaus/ABC
An Old Flame Returns
On Castle, just as Beckett decides to break things off with her current boyfriend to give it a go with Castle, he decides to spend the summer in the Hamptons with his ex-wife and publisher Gina. Sure, she just wanted him to finish his new novel, but some old flames are hard to put out.
Other examples: Henry's return just two episodes before Ugly Betty's series finale
6 of 20 Nicole Rivelli/NBC
Very Special Guest Star
Movie star Jennifer Aniston punctuated a season of not-often-seen-on-TV guest stars – Steve Martin, Alan Alda, and Oprah Winfrey, to name three — on 30 Rock. She played Liz's unreliable old friend Claire Harper, a hat designer who develops a fixation on Jack Donaghy
Other examples: Julia Roberts on Law & Order; George Clooney on Friends
7 of 20 Mario Perez/ABC/Getty Images
Modern Family wound down its Emmy-winning first season by relocating the Pritchetts and the Dunphys to Hawaii for patriarch Jay's birthday. Although the tropical island scenery was divine, it was the clan's gradual undoing at the airport that was the most fun to watch.
Other examples: The Brady Bunch's tiki-cursed trip to Hawaii, Full House's two-part trip to Disney World
8 of 20 Craig Sjodin/ABC
What to do when your narrative arc isn't working? Blow the whole damn town down, like Desperate Housewives did in Season 4 when a tornado struck Wisteria Lane. In one fell swoop, the show tied up loose plotlines, killed extraneous characters and moved the action forward in the quickest, most dramatic way possible.
Other examples: Earthquake on Modern Family; Hurricane on Dawson's Creek
9 of 20 Darren Michaels/Fox
It Was All Just a Dream
On the season finale of House's fifth season, it appeared that Dr. House was finally ready to have an adult relationship with Cuddy — or, at the very least, sleep with her. Their lovemaking made the hearts of fans of the coupling go pitter-patter, but there was one big problem: It wasn't real. Instead, the substance-abusing doc hallucinated the whole thing after popping a few Vicodin.
Other examples: One whole season of Dallas; the entire final season of Roseanne; Bones' coma sex
10 of 20 Justin Stephens/CBS
The Good Wife is a show about a woman, Alicia, who has to decide if she's going to stay with her ex-con husband, Peter, after he's implicated in a sex scandal. Complicating matters is Will, Alicia's handsome boss. What happens if Alicia isn't such a good wife after all? That was the question that the first season's finale posed — and continues to pose.
Other examples: Well, everyone on Mad Men for starters...
11 of 20 Cliff Lipson/CBS
A few weeks into its freshman run, NCIS: Los Angeles shocked audiences when rookie Dom was abducted and probably killed. The mysterious disappearance took most of the season to resolve, but not happily. Alas, Dom met his maker in a later episode.
Other examples: Well, there was that show Kidnapped. Walt was taken by the Others on Lost, and — spoiler alert! — keep your eyes peeled for an upcoming kidnapping on Hawaii Five-0.
12 of 20 The CW
Someone Gets Shot
At the end of Gossip Girl's third season, Czech muggers didn't care that he was Chuck Bass and shot him as he struggled to retain ownership of a very large engagement ring.
Other examples: Dallas' "Who Shot J.R.?" cliff-hanger; Uncle Junior shoots Tony on The Sopranos
13 of 20 Adam Taylor/Fox
After five seasons of will-they-or-won't-they tension, Bones chose an easy way to ensure that Brennan and Booth won't... for now: Booth returns from a tour of duty in Afghanistan head over heels in love with a war correspondent he met there. And as luck would have it, she followed him back to D.C! Poor Brennan.
Other examples: Beckett began dating Detective Demming on Castle, Andy came between Dwight and Angela on The Office
14 of 20 Byron Cohen/NBC
Despite their best efforts to prevent their lunatic families and coworkers from doing something embarrassing at their wedding, Jim and Pam's guests danced down the aisle in a hilarious homage to a viral YouTube phenomenon on The Office. Producers wisely intercut the wacky church footage with the happy couple's actual wedding, which took place hours earlier on the misty deck of a tugboat as it sailed under Niagara Falls.
Other examples: Lily and Bart on Gossip Girl; David and Donna on Beverly Hills, 90210
15 of 20 ABC
A Scary Diagnosis
Calista Flockhart delivered a brave performance in 2009 as her character, Kitty, was diagnosed with non-Hodgkin's lymphoma. As if having cancer wasn't enough, she had to suffer through it with a husband at her side who, just one season earlier, she came thisclose to leaving. After a few bad wigs (and the unexpected death of said husband), Kitty is still ticking.
Other examples: Brothers & Sisters also gave Holly amnesia this year, and Izzie's visions of Ghost Denny on Grey's Anatomy were explained away by her own case of lymphoma.
16 of 20 Ron P. Jaffe/Fox
Though it took them a while to get together, Barney and Robin's romance on How I Met Your Mother was painfully short-lived. Despite their mutual long-gestating feelings, they agreed that "two awesomes cancel each other out" and that they are better off as friends. Barney may be back as a suited-up bachelor, but it remains to be seen it these flames might someday be rekindled.
Other examples: Ross and Rachel on Friends is the standard-bearer that introduced "We were on a break" into the TV dating lexicon.
17 of 20 Bob Mahoney/The CW
Secret Identity Revealed
Gasp! Alaric's absent wife Isobel isn't dead in the conventional sense; she's a vampire. But what's this? She's also —gasp! — Elena's birth mother! (Jeez, The Vampire Diaries makes us gasp a lot.)
Other examples: Henry Gale is Benjamin Linus on Lost; Dana Walsh is the mole on 24; Don Draper is Dick Whitman on Mad Men
18 of 20 Jordin Althaus/NBC
A plane that just narrowly avoided crashing into the president's compound in Miami entered a wormhole and landed safely in the Arizona desert. That's where the trouble started for the survivors, who appeared to be summarily executed by a mysterious paramilitary force that landed shortly thereafter. But don't worry: the dearly departed of The Event's first really weird event (including pilot Michael Buchanan) woke up a few days later, basically unharmed, in an airplane hangar.
Other examples: Sayid on Lost; Noah Bennett healed on Heroes; Charlie Francis is alive on the other side on Fringe
19 of 20 Michael Desmond/ABC Archive/Getty Images
After spending much of Private Practice's third season with other partners, former friends with benefits Cooper and Charlotte find their way back to each other, more deeply. Cooper professes his love for Charlotte, who accepts his proposal.
Other examples: Don Draper's surprise question-popping to his secretary Megan on Mad Men's fourth-season finale; Jim's not-at-all-as-he-planned gas-station proposal to Pam on The Office
20 of 20 Sonja Flemming/CBS; Eric Liebowitz/CBS; Sonja Flemming/CBS; Robert Voets/CBS
For November 2009's sweeps, CSI's Laurence Fishburne worked a case about a prostitution ring that conveniently took him to visit Horatio Caine in Miami and Mac Taylor in New York. Ultimately, the case was solved back in Las Vegas.
Other examples: One Tree Hill and Life Unexpected merged for an episode this season. Grey's Anatomy and its spin-off, Private Practice are always swapping characters, but sometimes shows swap writers, like Two and Half Men and CSI did in 2008.