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A | Apartment Roller Luge
The game Robin invents to console Lily and Marshall over the slanted floors in their new apartment. Equipment needed: a skateboard, a metal salad strainer, and an open doorway.
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B | Blue French Horn
The instrument hanging in the restaurant where Robin and Ted have their first date. ''That horn is the pilot to me,'' says Cobie Smulders. ''We haven't made reference to it in so long. It's a Horcrux of the show.'' (For you non-Potter geeks, that means it's, like, super-important.) Now hangs in the office of co-creator Craig Thomas.
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C | Cockamouse
The flying mouse/cockroach hybrid that sets up shop in the gang's apartment. Also one of Jason Segel's favorite episodes: ''The episode makes me laugh like crazy,'' he says. ''We got to shoot it like it was a horror movie and overact, which I love.''
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D | Doppelgängers
Each of the gang has a ''twin'' revealed over seasons 5 and 6. Stripper Lily, Lesbian Robin, Señor Justicia (a mustachioed Marshall), Mexican Wrestler Ted, and Dr. John Stangel (Lily's fertility doctor, who's a ringer for Barney with a beard). Also the subject of Smulders' fantasy episode: ''I wish we could do an episode that is just the doppelgängers. Their lives would intersect as well. That's the show I want to watch!''
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E | Eighty-three
The number Barney always uses when inventing a statistic. Example: ''There is an 83 percent correlation between the times men wear boutonnieres and the times they get laid.''
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F | Fiero
Marshall's beloved Pontiac, which ends up in the Big Parking Lot in the Sky when it conks out just shy of 200,000 miles. A cassette single of the Proclaimers' ''I'm Gonna Be (500 Miles)'' is stuck in the tape deck. ''I love that you have all these flashbacks that fill in the blanks...which tell how everyone met everyone,'' says Josh Radnor of the episode, which is one of his favorites. ''There's something so sweet and hilarious about that.''
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G | Gary Blauman
Barney's colleague played by Smulders' real-life husband, Taran Killam. Blauman makes a public show of quitting his job by trying to pee on the conference table during a meeting. (Damn, pee shyness!) According to Barney, Blauman lost all his money soon after. ''Then he became a janitor at an old folks' home and moved into a one-room apartment above a bowling alley.... He died.'' Problem is that Blauman pops up again very alive in subsequent seasons. (And rumor has it that he'll show up in season 9.) A side note: Most of the cast's significant others have guest-starred on the series during its run: David Burtka, Neil Patrick Harris' partner, recurs as Lily's high school boyfriend Scooter, and Alyson Hannigan's husband, Alexis Denisof, appears as Robin's co-worker, blowhard newscaster Sandy Rivers.
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H | Hot/Crazy Scale
A graph created by — guess who? — Barney. The X axis represents ''crazy'' and the Y axis is ''hot.'' The goal is to date women who, when plotted on the scale, are above the diagonal.
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I | Interventions
After attending an alcohol-related intervention for their friend Stuart (Matt Boren) in season 4, the fivesome adopt the model to help one another kick other destructive habits — everything from Lily's ''weird fake English accent'' to Marshall's Dr. Seuss hat. A red-and-white banner is hung. Sometimes there's a poem. Or a pun. Also Radnor's favorite recurring gag. ''You can tell that the characters take them so seriously. They go to great lengths with the production value — like the banner comes out. The character never thinks it's for him or her — but it always is.''
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J | James
Barney's gay half brother, played by Wayne Brady. In this season's opener, watch for James to perform the most amazing/disturbing wedding number aired on TV.
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K | Karate Kid
Toward the end of season 8, Barney is disappointed when the gang invites Ralph Macchio to his bachelor party instead of the ''real'' Karate Kid, Billy Zabka. But at the end of the half hour, a clown wipes off his makeup to reveal he's actually Zabka. ''The '80s have this weird canonical importance to us,'' says co-creator Carter Bays. ''The first time I saw Zabka there was a feeling of 'Oh, s---, this guy is going to beat me up.' But then you meet him and he's totally cool.'' Meanwhile, Hannigan had her own fan moment: ''There was hardly any acting required on my part when I was obsessing over Ralph Macchio.''
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L | Legendary
First uttered by Barney in season 1, episode 3. Best variation: ''Legen — wait for it, and I hope you're not lactose-intolerant 'cause the second half of that word is — dary.''
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M | MacLaren's
The neighborhood bar is a second home for the gang. Based on McGee's in NYC, it employs bartender Carl MacLaren (named for Carter Bays and Craig Thomas' former assistant; played by Joe Nieves).
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N | ''Nothin' Suits Me Like a Suit''
In the show's 100th episode, Barney must decide whether to give up suits in order to bag MacLaren's hot bartender, played by Stacy Keibler. He chooses his suits over his suitor. The episode ends with a pull-out-the-stops musical number — an homage to Gene Kelly's ''Singin' in the Rain'' (minus the precipitation).
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O | Ohio
The home state of Ted and his real-life alter ego, Bays. Says Radnor: ''One of the greatest lines I ever got to say on the show was [in season 2, episode 17] when Marshall asks Ted, 'You live in Ohio, right?' And Ted says, 'My parents live in Ohio. I live in the moment.'''
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P | Patrice
Robin's persistently chipper co-worker/nemesis at World Wide News, played by Ellen D. Williams. Target of Robin's wrathful catchphrase ''Nobody asked you, Patrice!'' which some complete genius has set to a techno beat and posted on YouTube. Smulders was reluctant to carry out this gag at first. ''Ellen, who plays Patrice, is the sweetest person on the planet. She literally just gave me a gift bag of coloring stuff for my child. She makes things for our crew. She kind of is Patrice,'' she says. ''I had a hard time with Patrice. I needed a pep talk from the writers. They were like, 'It's totally fine. Patrice is that one person in your life that you can't stand and you're totally in the wrong about it. It's human behavior.' It was so heartbreaking to yell at her. But I really like having Ellen on the show, and if yelling at her means we get to keep her, that's great.'' Patrice's photo is pasted on the bay of monitors that the director and writers watch when filming. She'll return in season 9.
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Q | Quinn
Barney's stripper fiancée in season 7, played by the terrific Becki Newton. ''Quinn's'' is also the name of the restaurant where Ted picks up wings for the gang's Super Bowl party in season 2. ''That's a surprise to me!'' says Thomas. ''That's just Carter and me liking the name. It wasn't some amazing call forward. Actually, Carter and I have a screenplay that had a character by that name, too.''
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R | Robin Sparkles
The gang discovers, much to everyone's joy, that Robin was a teen pop star in Canada. (Thanks, Alanis Morissette, for the inspiration!) Her one hit, ''Let's Go to the Mall,'' is an '80s-inspired bonanza. Follow-up flops include ''Sandcastles in the Sand'' and the edgy ''P.S. I Love You'' (as Robin Daggers), which recounts Robin's unrequited obsession with Paul Shaffer. ''Being in a recording studio, where I never find myself, it was a great change of pace,'' says Smulders. Sparkles' band is stuffed with current and former HIMYM crew, including Matt Kuhn on drums, Jamie Adamic on keytar, David Baker on guitar, and the real Carl MacLaren on keyboard.
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S | Slap Bet
Following an elaborate series of bets you'd need a Ph.D. in slapology to understand, Marshall wins the right to wallop Barney a number of times across the face. The show went to town with this, even creating a Slap Bet Countdown (theslapbetcountdown.com) timed to the third slap. ''One of my favorite things in comedy is when something has been so intricately constructed that is so fundamentally dumb, and I think the slap bet is like that,'' says Thomas. ''We've made this entire mythology.''
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T | Two-Minute Date
Comely dermatologist Stella Zinman (Sarah Chalke) complains she has only two minutes for lunch, so in season 3 Ted takes her on a two-minute date, complete with a cab ride, meal, and movie — all filmed in one take. Bays explains how a show known for its quick scenes pulled this off: ''The day of shooting it felt like orchestrating the moon landing. It was fun seeing everybody working like a clock. The final product was this sweet romantic moment,'' he says. ''If you pick two minutes of the entire series that tell what the show is, I'd select those two minutes.''
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U | Urinal
Where Ted and Barney met for the first time in 2001.
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V | ''Vomit-free since '93''
Ted's upchuck-free boast...which turns out to be false.
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W | The Wedding Bride
A film by Stella's ex-turned-husband, Tony Grafanello (Jason Jones), depicting the love triangle involving Stella (Malin Akerman), a saintly Tony (Jason Lewis), and Jed Mosley (Chris Kattan, hysterical as a louche version of Ted). The fifth-highest-grossing movie of all time and Kim Jong Il's second-favorite film. In a flash-forward from season 7, Ted first professes his love to The Mother in front of a theater playing Wedding Bride III. ''I really liked the redundancy of the title,'' says Bays. ''I can't remember if this joke made it in, but the idea was that it was from the makers of Police Cop.'' It didn't, but it should have.
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X | X, Dr.
Ted's underground ''secret'' radio persona at Wesleyan University.
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Y | Yellow Umbrella
The talisman of the show, dreamed up in what Bays calls the ''very fertile'' stretch in 2008 after the writers' strike. Ted and The Mother attend the same Saint Patrick's Day party in season 3. When Ted goes back to find his lost phone, he picks up the umbrella The Mother left behind to shield himself from the rain. Seasons later he returns it to The Mother, forgetting it at her apartment after a chat with her roommate, Cindy (Rachel Bilson). The color of the object, a sharp contrast to gray New York City, wasn't an accident, says Bays. ''There are a lot of objects in primary colors on the show: the blue French horn, the red cowboy boots, the yellow umbrella. If there's a spin-off of this show, it will be in the form of a children's cereal.''
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Z | Zoey
Ted's girlfriend in season 6 (played by a post-House, pre-Once Upon A Time Jennifer Morrison), who opposes his plans to tear down the Arcadian hotel for the new Goliath National Bank headquarters. Just for kicks, click through to check out our list of the rest of Ted's 20 other girlfriends (courtesy of the HIMYM office).